If America's Funniest Home Videos taught us anything, it's that traditional bike wheels will put amateur cyclists on a direct collision course with whatever's directly in front of them. The Sperovelo Rider seems like a much better option for kids, since its large spherical wheels let it move in any direction, and more easily avoid a crash.
A pair of omnidirectional casters serve as training wheels, and can be removed when young'ns get the hang of riding the Sperovelo. But they also prevent it from just toppling over on its own, so you may want to leave them attached no matter what. At a buck shy of $100 the Sperovelo isn't terribly expensive, either, especially if its unique design helps prevent it from bouncing off and destroying all the furniture in your home. [MoMA Store]