I generally tend to shy away from items like this, but my wife talked me into buying one (actually one for each of us). Well, let me be the first to say, these things are FANTASTIC! They are little electrode patches that you place on certain muscle joints and plug into what looks like an mp3 player.
There are 6 different cycles to choose from and you also select the strength of the treatment. I've been keeping mine on around 3, which is plenty riveting enough for me. The electric pulses twitch and pull at your muscles and it somewhat simulates an actual massage.
After a long day of walking down the Vegas strip, we rested back at the hotel for a short span while we placed these on our aches and pains. And in no time at all, we were ready to go again! Easy to follow instructions, and they recharge using a USB port.