LoJack for the Rest of Us

October 20th, 2004

Why not use wi-fi (wireless Internet) access points to track down stolen cars, bikes, purses and other valuables?

Many of Earth’s major cities are becoming saturated with wi-fi access points. It’s hard to find a public place in San Francisco, for instance, where a wi-fi device can’t detect a nearby access point.

Imagine placing a narrow wi-fi beacon device inside the frame of your bicycle. You tell the beacon that, every day at 4 a.m., the bike is locked up at your house. Next time the clock strikes 4 a.m., the beacon turns itself on and it makes note of which wi-fi access points it can “see” from your home. It remembers that these access points represent home. Then it turns itself off again. (Wi-fi detection drains a lot of battery power — the device stays off most of the time to save juice).

Two days later, at precisely 4 a.m., the beacon powers on and notes what access points it can “see.” If it detects one or more of the “home” access points, it turns itself off again. Two days later it does the same thing, and so on. We’ll call this state of affairs the beacon’s default mode.

During one of these early-morning access-point checks, if the device doesn’t detect a home access point, it switches into “stolen mode.” It powers on every 15 minutes and checks for any open access points. (Open access points are not encrypted, so anyone — and in our case, any beacon — can use them to connect to the Internet.)

– – –

When the device finds an open access point within range, it sends a message to a server. The message specifies which beacon sent it, as well as a unique identification number that specifies which wi-fi access point is being used. The message also includes a list of other access points that the device “saw” during its recent travels.

Software on the server connects to a database that stores the geographic locations of known access points. It uses this information to convert the list of access points recently “seen” by the beacon to a path on a map illustrating your stolen bike’s recent movement. It converts the beacon’s current access point to the beacon’s current location, which it marks on the map and converts to a street address. The server sends this information to your e-mail account — and to the police, if that’s what you want.

(Each time the beacon connects to the server, it also checks for commands that it’s supposed to follow. Via a password-protected Web interface, you can tell the beacon to switch from “stolen” mode back to default mode. You can set a new home location, and you can set a new time for it to check each day for its “home” access point fingerprint.)

This would provide essentially the same service offered by LoJack, an extremely expensive anti-theft system for cars. LoJack depends upon a beacon that’s hidden in a car. If your LoJack-equipped car is stolen, when you file a police report a radio signal is sent to the beacon that puts it into “stolen” mode, which causes it to repeatedly emit a signal over a special radio frequency. Police cars and aircraft equipped with special LoJack sensing computers can track this signal and follow it to the car. LoJack is quite expensive ( sells the device for $695, for instance), and the real expense comes from the service: LoJack employees and police have to be trained to use the tracking equipment, and so on. (Other services based on Global Positioning Satellite and cellular phone systems are also quite expensive.)

Now that wi-fi is almost ubiquitous in many areas, we can create a system that allows people who live in those areas to track their stolen goods without LoJack and all of its overhead — at a tiny fraction of the cost.

But remember that new stolen-item-tracking technologies can be put to darker uses too. Such developments mean that almost anyone might have the power to plant tracking devices on unsuspecting people and vehicles.

25 Responses to “LoJack for the Rest of Us”

  1. comment number 1 by: Simon Cox

    Right, next time I nick a bike to get home from the pub I will have to wrap it in tin foil when I get home.

  2. comment number 2 by: sean

    Now Mr. Cox, I think you know that wi-fi works through tin foil. I’m afraid you’ll need to put your home and bikerack underwater.

  3. comment number 3 by: Simon Cox

    OMG! That means the government IS making me do things I don’t want to. They must be using wifi to get through my foil skull cap… Aaaarrggh!

  4. comment number 4 by: Robert

    Imagine your at a college and someone steals your bike. With your system you might go from seeing 3 access points when its “home” to 7 or more, including your original 3 when it is stolen… Where is your bike?

    I’d like to see a GPS+WiFi system that reports its location to a central server (email?) daily through the nearest open access point, and checks the server (webpage?) to see if it should go into “stolen” mode and start reporting more frequently…

  5. comment number 5 by: sean


    I’m missing your point. Why would the device still see the 3 “home” access points if it’s been stolen and is no longer at home?

    I GPS device added to wi-fi would suck a lot more battery juice and would be a bigger problem to conceal and still have it receive satellite signals.

    Basic location determination via wi-fi is viable; see for instance.

  6. comment number 6 by: Anonymous

    if it is in a room down the hall.

  7. comment number 7 by: Adam Jacob Muller

    GPS+GPRS/1xRTT would be nice…

    I can GPRS with my phone for about 5 hours on single charge. GPRS’ing for 5 minutes a day to report location gives me 60 days of battery life. Plus, you could fit a much larger battery in a bike.

  8. comment number 8 by: Adam Jacob Muller

    Oh, and I do location detection using wifi. Check out

    It tells you where I am based on what network my laptop is connected to.

  9. comment number 9 by: darkonc

    If it’s so close to it’s ‘home’ location on a regular basis that it’s seeing all of your ‘home’ wifi stations, then I expect that you’ll be seeing it yourself pretty soon, and able to collar the thief within the next couple of weeks.

  10. comment number 10 by: Sean

    you said it darkonc.. If someone steals your bike but keeps it within 300 feet of your house, I’m betting you and the thief have other issues..

  11. comment number 11 by: mike

  12. comment number 12 by: Andrew

    I’d like to see the bike log into a jabber instant messenger server and ping my account with the IP address of where it “is” each time it finds an open access point. Then if I’m on-line (and hence not on the bike) I’d know if my bike was on the move… and where, broadly found by the ipaddress’ physical location via, or possibly gps for better resolution.

    I’m making maps of devices on the web via their ip adress (recently network cameras) and it works well – but tracking moving things would be great.

    Check out to see the maps.

  13. comment number 13 by: Sean


    Great geohacking you’re doing there!

    RE: IP addresses – that’s good for networked cameras to be mapped across a world map, but can this provide the specificity of location that you’d need to find a stolen item in your neighborhood? And what about the many access points connected to dynamic-IP service? Access point mac addresses don’t (generally) change and locations gathered from wardrivers and mapped to mac addresses provide the specificity to say: access point X is within 300 feet or so of location Y.

  14. comment number 14 by: Andrew

    Thanks Sean. “geohacking” – I like it.

    Ok – gps unit problems aside from previous commentary – if the device on the bike had a gps unit, it could also transmit all *logged* locations of where it had been for the last 2 weeks or so in detail. So the thief’s home details could be havested in that waypoint file, revealing much more info about the thief, which is better than only the current location in terms of catching them, and also in prosecuting them.

    Imagine the courtroom…. “Repeatly the bike was located at your home for the last week…” is pretty damning.

    If that could be done using placelab even better.

  15. comment number 15 by: sean


    I think you and I are saying almost the same thing. I’m just saying you don’t need GPS to do it; wifi is all you need.


  16. comment number 16 by: sidhbhra



    MAKE living WORTH it

    MAKE A statement

    Give VENT to your CREATIVITY

    You are not ALONE


    CAMBIA il MONDO sottilmente


    DI’ la TUA


    non sei SOLA/O

    Definition: flash mob (FLASH mawb) n. A large group of people who gather in

    a usually predetermined location, perform some brief action, and

    then quickly disperse. –v., –adj.

    –flash mobber n.

    –flash mobbing pp.

    A new group for Dublin and Milan…join up.

  17. comment number 17 by: daniel r luke

    Here’s what I’d like to see. You ride around all month long on your GPS equipped bike, and as a result you generate tons of geolocation information based on where you’ve been. At some point it will be possible, using this information, to determine how much time each week you spend doing your laundry, how much time you spend at home, or at the local pub, etc. I would like to see this information put to use to measure compatiblity in some kind of dating service. You could, for instance, match your geolaction profile with someone else’s.

  18. comment number 18 by: Erich Schubert

    They’ll probably just remove the device…

    Here recently the very expensive *armored* Mercedes of the Daimler-Benz boss was stolen.

    It contains about every feature you can imagine, including GPS for finding it. They left it in a parking lot for 20 minutes they claim.

    So apparently, an expert (admittedly) can remove a GPS unit out of a high-end armored Mercedes in less than 20 minutes and steal the car.

    But when you hide a wifi unit in the bike, how is it powered? you can probably just either cut the power wires or put too much power on them to fry the electronics. Or maybe even pull it out. Or pour something in there.

    Also the wifi unit may easily be damaged in there, due to water running in, extensive shaking etc.

    Of course it will help against the typical asshole who just doesn’t want to walk, which makes up probably for 99% of stolen bikes. But he’ll probably just throw your bike into a river or so anyway.

  19. comment number 19 by: C Peril

    If you live in a dense inner-city neighborhood your bike could easily be stolen and still have the same 3 WiFi points. If bikes are stolen here in San Francisco the guy on the next block could easily hold on to your bike without your ever seeing it — and it would triangulate to the same three coffee shops.

    The person who posted about a college campus has a similar point. If you’re in a big housing complex (dorm, project, etc.), someone IN YOUR SAME BUILDING can steal your bike and paint it before you even know it’s gone.

    Shitty, yes, but it happens all the time.

  20. comment number 20 by: sean

    Erich: The device would have to be powered by battery, and HIDDEN in the bike.

    C Peril: Right, if someone steals your bike and takes it to a place less then a couple hundred feet from where it normally is locked, this won’t help you that much. I suppose if this is ever made, the manufacturer should put a big warning on the box: “WARNING: This device will only be very effective in the vast majority of cases of bike theft wherein the bike is taken more than 200 feet away. In cases where the bike is less than 200 feet away, you’ll only know that it’s less than 200 feet away. Please do not sue us in such cases. For chrissake, get to know your neighbors.”

  21. comment number 21 by: Rick

    Steve Wozniak is already working on a similar idea which uses GPS satellite technology to determine the transponder’s location

    At wOzô our mission is to deliver a wireless platform that helps you know where something is regardless of where you are. Using a breakthrough wireless network, wOzNetô, and advanced GPS technology, the wOz Platform enables a range of solutions for consumers and businesses.

    Know where your loved ones are

    Find them when they aren’t where they should be

    Get proactive alerts when they leave or return

    Track containers, equipment and personnel

    Locate items without costly readers

    Get status information online from any location

  22. comment number 22 by: sean


    Again, GPS receivers are more expensive, suck more battery juice and require line-of-sight access to the satellites (i.e., part of the beacon would have to be outside your bike, and it wouldn’t work when you’re bike’s under a ceiling or overhang). Those are three reasons why wi-fi is a superior solution; si?

  23. comment number 23 by: lojack

    i work for lojack and you are completely oversimplifying the process. Unlike those othe systems, lojack can run off its own energy if the battery is removed from the car and is very difficult to locate in a car. Those other systems shut down if voltage is removed. also, gps does not work underground and in containers. but radio frequencies can stil be emmitted. the service is worth the fee.

  24. comment number 24 by: sean

    To “lojack,” the Lojack employee:

    Here’s why the points you make are invalid:

    RE: voltage being removed — a bike has no central electrical system, so this system would rely on batteries attached to the transceiver, which is hidden. So thieves would have just as much trouble powering down this transceiver as they would powering down a lojack transceiver — i.e., you’ve got to find it first.

    RE: GPS limitations — The system I suggested doesn’t use gps at all, so why are you pointing to GPS limitations?

  25. comment number 25 by: Persephonii

    Would make stalking ever more efficient. *shivvers*
    My computer geek ex would do whatever to taste it again…