Since the Segway merger, I've been a bit more interested in Segway's Ninebot One E+ "self-balancing one-wheeled scooter".
Apparently Amazon's algorithms noticed this. Today I got an add for Ninebot One "training wheels":
http://www.amazon.com/dp/B00S67UES2/
Okay, now I'm interested. I watched this video of a guy riding a Ninebot One up a sidewalk on a hill in San Francisco. I don't know how practical it would be...but it looks kind of fun.
None of these "new" Ninebot machines look like they're nicer machines than the I2, but the new MiniPRO is really interesting from a "small and light" perspective--and the One E+ from a "hey that could be fun to play on" perspective.