I enjoyed this week’s discussion of the device someone had hidden in a car that would call out “words of wisdom” (usually, profanity laced) as it rattled wherever it was hidden. The caller was trying to locate and remove it.
You mentioned it might be good to get “revenge”, and I have a suggestion: it’s called the Annoy-a-Tron (Thinkgeek.com - no connection with me, except I got one free at a tech conference recently and can attest that it works) and it emits, at random intervals, sounds at 2 or 12KHz. It’s designed to be hard to locate. I’d get one and hide it somewhere…perfect revenge.
Or you could get an MP3 player and load it up with old Car Talk podcasts before concealing it.
Reminds me of the line from the movie Dumb & Dumber. “Hey, wanna hear the most annoying sound in the world??” 
Back in high school I got revenge for a practical joke pulled on me by wiring the little jerk’s left blinker to the horn relay. Took the guy a month to figure out why the hell the horn honked every time he wanted to turn left.
I have seen that, but have not found the perfect application, in the olden days we would just put some Limburger cheese under the seat!
Took the guy a month to figure out why the hell the horn honked every time he wanted to turn left.
Not the brightest bulb in the box was he?
No. Which was fortunate, because it let me win a lot when we got into joke wars 
It sounds like you need the automotive equivalent of this http://thedilbertstore.com/products/70602-phantom-keystroker-v2