Hello all! I was just wondering if anyone thought it was possible to use the n900 as a car key remote? I just thought it would be cool if this could be implemented in some way either with or without extra hardware. I own a car from 1997 and the range was never that great...

I got off wikipedia that these keyless entry systems use radio waves (315 MHz in US) to lock and unlock the doors. Maybe this or bluetooth technology could be used. I think this may prove to be unfeasible as data from the car's computer may be needed which may be too much of a hassle....

Would be cool to use the n900 as a garage door opener too :P
Any ideas are greatly appreciated!

This wont be possible, using your car's standard remote unlock - Regardless of whether the N900 can broadcast on the correct frequency, the rolling code algoritm used to send the correct unlock signal will only be known by the car's manufacture and will be hard-coded to the specific car's ECU - Some older cars did use very weak security before rolling codes were standard, but even in those cases I doubt the exact algorithms to beat the code are in the wild.
It'd probably be far easier to put a computer into the car either connected to the internet via 3g or with a secured ad-hoc wifi connection available and connect to it either via the net or directly from your n900, with the computer running your own software to hook directly into the car's door openers. A pretty complex hands-on diy project, but definitely doable.

Great thanks! That's all I needed to hear! Yeah I knew this wouldn't be that simple, I'm gonna look into it a bit more.

WAIT!

From wikipedia:

Remote keyless entry fobs emit a radio frequency with a designated, distinct digital identity code. Inasmuch as "programming" fobs is a proprietary technical process, it is typically performed by the automobile dealership. (In point of fact it is a computer in the car which is programmed in the process, not the fob itself.) In general, the procedure is to put the car computer in 'programming mode'. This usually entails engaging the power in the car several times while holding a button or lever. It may also include opening doors, or removing fuses. The procedure varies amongst various makes, models, and years. Once in 'programming mode' one or more of the fob buttons is depressed to send the digital identity code to the car's onboard computer. The computer saves the code and the car is then taken out of 'programming mode'.

So could the n900 be used to emit the radio frequency code? I don't know if any dealerships would comply with this but it would be worth a try. Of course the problem with this is that the key fob then would be useless....which isn't ideal

No - The fob does emit it's "code" as it specifies, but all that actual code is is effectively just the unique hardware identifier of the fob - much the same as pairing most other wireless devices, which is what the process outlined in the Wikipedia article does, essentially just the pairing of fob and car.
However, the fob itself must still be programmed with the secure rolling code random number generator used by the manufacture, so that the fob and car store the same codes for each use (the codes have to match at both the fob and car in order to work) and it's this bit that's propietary.
For more detail that's pretty simple to read, see:

http://auto.howstuffworks.com/remote-entry2.htm

Not really what you're asking for... but I remember reading about using a cheap prepaid cell phone as a remote start / lock receiver on instructables.

This can be done in many ways. first check out my thread on "controlling relays with n900" im doing this right now using N.C.D usb 24 relay board connected to a mico atom pc in my trunk and remote desktop 1.7 on my n900. check these sites out and see if it helps. addition hardware will be needed.

remember all of this works separately from your car door lock, security systems.


http://talk.maemo.org/showthread.php?t=47390

@nidO: thanks for bearing with me, i should have done some more research before asking this

@knowpow: thats pretty cool i will check it out!

Just commenting on this thread, most OEM manufatcures have just started using rolling codes. To verify if you have a rolling code, try program your key fob with a universal remote.I think pre 03 were standard codes, remember showing someone with a Benz S class how to unlock his doors and trunk with a Harmony remote.
But, I think the emitter would not be strong enough to work from any real distance.

How do you program the key fob with a universal remote? Yeah my vehicle was from 1997...

Yeah the emitter not being strong enough is also an obstacle.