We use a portable electric fence for our fly-in moose camp(talked about in Mudster's thread earlier). It is very compact and runs on 6 D batteries. We cover an area of approx. 100' x 50', so our tent and meat pole are within it's perimeter. The jolt does not seem to be very powerfull, but I still manage to shock Pierre every year when he is setting it up!
Does it work? I don't know, but we have used it on five trips, for a total of 10 weeks, and haven't had a bear in our camp yet. It's just an extra precaution we take to keep our tent, meat, food, and ourselves safe in an area where help is a long ways away. It would be neat to watch a bear approach it and see what happens!