Tool blog Toolmonger has just turned me on to a nifty little gadget that could offer many of us road-trip enthusiasts a better sense of security on the road. Called the Wedge Alarm, it's a simple little 110dB noisemaker that's designed to fit temporarily under the edge of a door or window and notify a room's occupants of any unauthorized entry.
Now, it won't do anything to keep burglars from making off with your luggage while you're out of your motel room, but as someone who has stayed in some pretty sketchy places, I can say that I would certainly sleep a little sounder in certain motels with this thing wedged under the door.
According to Google, you can pick this one up, or a model similar to it, for as little as around $4.