I've always thought those things were a bad idea. If you are healthy, it is the last thing you need. If you need a motorized wheelchair, a segway is not going to be able to help you. It only makes you weaker and costs you a lot of money and opens up the possibility of the occasional face plant. No thanks.
I've seen a few security officers driving them around the local mall while on duty. I don't understand why they need them... They also cost ~5k don't they?