Cheap GPS car alarm?

After looking at local prices of GPS stolen car finding systems (1000$ for installation + 50$/month) I thought it'd be much cheaper to make one.

So basically one needs Arduino with GPS shield/receiver and GSM modem. Sounds too simple. May there be something else?

Estimated costs: EM-406A GPS receiver 60$ (Sparkfun) GPS Shield 15$ (Sparkfun) +shipping Arduino board 20$ GSM SIEMENS TC35 SMS Module UART/232 29$ (ebay)

Total: ~130$ +battery, SIM, phone bill.

Am I missing anything?

Am I missing anything?

The sticker to put on the steering wheel to tell the thief to turn the device on.

maybe keypad or some sort of command (rfid,bluetooth,wireless) that youll let your arduino know your the owner of the car and not the thief


Am I missing anything?

The sticker to put on the steering wheel to tell the thief to turn the device on.

I was going to add one more thing to the list but thought it won't be good for everyone. My idea is that the device is ON constantly and starts to transmit coordinates whenever the car starts to move, unless it senses the presence of drivers key-chain RF transmitter. Transmitter/receiver would be Arduino nano/mini with one of those 10$ ebay 333/433Mhz RF links - sending a signal, say - once a couple minutes, to save battery. But that's only an option and not the most convenient one. I just have some experience with those RF and none with bluetooth.

As putyn suggested, maybe it is possible to use phone bluetooth, to do the same?

As putyn suggested, maybe it is possible to use phone bluetooth, to do the same?

Suppose you leave your phone in the car, for a day at the beach. What happens when your car leaves without you?

not sure if you need to keep your device always on , you could tell the arduino that you started the car using an external interrupt and allow 30-60s for the driver to "authenticate" himself bluetooth should work but youll need to develop your own application since im not sure youll find one already built easiest solution since your already in the car (and you dont need long distance transmission) would be to use some cheap transceivers (

or if your car has a central locking system that uses a remote control you can use that remote to trigger a pattern (since when you lock/unlock the car the your turn signals blink) and arduino will "listen" for that pattern if it will receive the pattern the driver will be successful "authenticated" this project ( uses the remote control to power up/down a heater in the car but the source code its written in assembler

Remote key locks use strong encryption, they should never transmit the same pattern twice.

Perhaps you simply need a notification everytime the car moves off, you can ignore the one’s you are reponsible for - still costs a little, but
cheaper than commercial devices I bet :wink:

You then want a remote way (SMS?) to switch on full tracking when you notice its stolen. So long as the car is somewhere with a signal and the thief hasn’t found and disabled your device, you can track it. It also serves as a good test-mode.

Boost Mobile Motorola i296: $49.99 Tracking software and service from Free

You’re over thinking it. If the device is going in the car just set it up to send you the coordinates when you request them. I just finished a similar project ( that can be adapted to a car (which is my next project).

If you’re going to leave it on all the time then you’ll need a battery backup and charging circuit to recharge the battery. The problem with leaving it on all the time is that the GPS and GSM consume a lot of power so you’ll need to account for extended periods of time when the car is not running and able to recharge the battery. If the GPS antenna is in a semi visible location, you can conserve power by having the GPS powered off until you are ready to retrieve the coordinates.

I also recommend using prepaid SIM cards that can be reactivated immediately upon refilling them. I use T-Mobile and the SIM is reactivated as soon as I refill it online with my credit card.