I saw a cop on one in the airport once. I thought that was a pretty good use for one. It would be HILARIOUS just to see a cop put a hurting on some pick pocket or some such by chasing them down on a segway.
One of the University of Louisville cops has one. Its funny watching him cruise around Papa John's Cardinal Stadium at the football games. It looks like he should fall off. I'd like to try one just to see what it is like. It looks like you would fall forward or backward if you aren't careful.