Put a door/window sensor at 'dog level' and a huge magnet on his/her collar
Sorry, had to...
How 'bout that hacked motion sensor. Expose the wires off the cds cell. Put some tasty stuff
on it for a couple weeks. Teach the dog to lick the goop off. Eventually, he/she will learn to
lick the sensors and key up the tranmitter. Even old dogs can learn new tricks.
Of course, we have to hope that the dog's saliva salinity is enough to trip the circuit.
How's that for a crazy idea?
Oh, and we don't need to involve PETA. It's probably only uVolts.