car alarm
Otherwise you'll have to design it; which if you have an electronics experience should not be hard at all.
I have had it for over a year now and I'm very satisfied. You can't tell that it's not from the factory. The unlock button unlocks the doors and turns off the alarm while the lock button locks the doors and sets the alarm (or you can program the alarm to arm automatically). If you do the progressive door lock mod, you can also use the second channel for an option such as power window control - still using the factory key fob.
Edit: BTW, you can find it online for about $75.






