Hate to be the buzzkill and the gadfly (nah, I relish in it) but...
That's illegal and all those people are open for a lawsuit. While fun, I'd think twice before doing this. It falls under "booby trap" laws most definitely, and probably even if they were warned beforehand. The thief could easily claim (reasonable doubt) that they were just taking it to return to owner (now they are the victim). We found a phone and did just that recently, returned it to the owner (well, management of the restaurant they left it in). If you'd popped me with current, god fucking help you when you crawl out from under your rock to claim it. I'll call police, an ambulance, get a full checkup and then bill all that plus pain and suffering, win in court and walk away with your house.
Personally, I believe properly constructed booby traps on your own property that are SAFE otherwise should be legal, but they aren't in the US. I spoke with (ATI?) some company about using Clear-Out for an active security system that I wanted to market at the time. They'd only sell it at first with a waiver, then changed their minds and didn't want their products being incorporated into the system. That was WITH prior warning! Too much lawyer shit kept me out of it. Doing this in public? Uh-uh.
What does work and isn't illegal to use are GPS tags. You can hide 'em in items likely to be stolen and they go active when they stray from the property, link to any cell phone they can and then transmit location. Only downside is that it requires cell phones that have the application for it to communicate off it. Would be nice if they could link to cell towers instead.
