The Magnetix iCoaster (or "I-Coaster" depending on who you ask) is the latest incarnation of the old "marble rollercoaster" concept, this time with a heavy emphasis on magnets and music. The music aspects are actually the least interesting: you can plug in an iPod to listen to music on its probably-not-so-great speaker, or trigger sound effects when the steel marble passes through certain gates.
The magnet tricks, on the other hand, seem nifty. The ball is taken to the top of the coaster on a "magnetic elevator." Certain segments drop the track but leave a magnetized side rail that carries the ball across. The track pieces themselves actually clip together by magnets.
The whole kit is $80. The only review on Amazon is broadly positive, although they do suggest that completing a successful circuit of the coaster can take some patience. (I consider that a feature, not a bug.) I just wish you could ditch all the music parts and get extra track and trick segments instead.
Catalog Page [Amazon]