I went on a Segway today, and it was rather fun. The problems with the Segway are:
1. You can't legally ride it on a public road
2. You can't legally ride it on a public pavement
3. It's *very* heavy, so if I took one out geocaching, the first time I'd need to lift it over an obstacle, end of trip.
4. Cost is about 7000 pounds
So the only place I could ride it would be around my back garden, which isn't big enough.