Hamster Wheels for Kids?

Do you know what I think would be a great invention?  Kid-Sized Hamster Wheels.  Seriously. 

Our old house was laid out in a line, all the rooms connected in a straight line.  Although the kids would sometimes run back and forth, the doors weren't lined up and the stairwell jutted out into the track, so in-house running wasn't that popular.  Even if I had said, "Sure kids, please feel free to run around the house as fast as you can. Enjoy yourselves!"  The kids couldn't really have come up to speed and there was just too much zig-zagging.  Not good.

Our new house, however, has an apparently marvelous loop track (entryway to living room to hallway to entryway).   The most popular exercise time is after dinner when Scott and I are still chatting at the table and the kids have been excused.  They just start going and going, round and round and round.   I didn't have an indoor loop track growing up, so I'm not sure what exactly the attraction is, but clearly all 3 of the kids can't get enough.  Generally, the running is coupled with scaring the wits out of each other,  numerous costume changes, and/or Star Wars sound effects.

While I guess I'm ok with this activity, provided no doors or tackling is involved (it is exercise after all), I think it's a shame we can't put them on a Kids Hamster Wheel or something.  The kid's wheel could even be wired into the power grid, like a solar panel.  Then, the kids could power a few light bulbs on their after dinner zips.  Just a thought....