Inside the car perhaps. I think I misread your original post. I thought you meant the outside handles. Big difference. Outside there's no way as there are any number of scenarios where someone could get hurt without trying to break into your car.

Still, you might want to go one better than a cousin cop for interpreting legal standing. Not knocking your cousin, my brother's a cop, I often ask him questions on mods, but he's not a lawyer. There might be less well know laws that could snarl you. Also, you could still get sued if someone got hurt.

The other thing is, unless your an engineer, and something goes wrong, you again, are probably *****ed. Like say you get shocked while driving and cause an accident.

The last thing to think about is making sure you dont' fry your car. My car for instance has the door handles connected to an ECU. With that voltage, it arcs. You put this on your inner door switches, you might end up frying your electrical system.

edit
One more thing. Make sure to install a camera/DVR with the alarm so you can have it on tape if it does work. That would be great