Segway--I have had one for 18 mos. It has allowed me to commute to work, shop. and generally get more relief from fatigue which has added more hours to my days.
Balance is a problem sometimes when walking. I am mentally trying to figure out how I could balance on a Segway. When my muscles mis-fire or I lose my balance, wouldn't the Segway misinterpret it and do the wrong thing? Does it not get tiring just standing without walking? I have problems pressing the gas pedal for any length of time and am so thankful for cruise control. They look useful and fun though.
I saw them (not too close though) in use at Disneyworld at Christmas this past year by some of the park workers. Never did ask the question as to whether visitors could bring their own, but having read an article in the newspaper earlier in the year that they could not made me curious.