Lumi Keys uses its individually illuminated keys in conjunction with an app for Android and iOS to teach you songs, scales, and the fundamentals of music theory.
It's like Guitar Hero... except with skills you can transfer to an actual piano. The keys aren't full-sized, but at ⅞ the width of standard ones, they're not far off. They’re also not weighted like real piano keys, but then, few keyboards under $500 offer that.
Crucially, though, the keys are pretty responsive and, generally, if I miss a note it’s me — not the Lumi Keys — that’s to blame.