I have the best cheapest anti theft device available.
I live downtown and park my bike on the street instead of the underground, which most people think was crazy, but I have the ultimate in bike theft prevension.
I call it the "Bike Buddy" The bike buddy is this homeless guy that sleeps next to my bike. I call him "buddy" he calls me "buddy". I give him all of my empties and now and again bring him some hot food in those disposable containers.
The guy loves me, and no matter how hammered he may get, the Vance and Hines ALWAYS wakes him up.
Try to jack my shit now bike thieves!!! No way your getting pat BUDDY!!
Edit: Hopefully no one throws out a mattress somewhere else or I am totally fucked!