Bill Wesley from San Diego has taken the 'Thumb Piano' (which is a bad name for a bunch of different African instruments, including the Kalimba) and pushed it. His Array M'Bira has up to 150 indivdually made and tuned carbon steel tines, soundboards made from various exotic woods, and lots of nice engraving. That's probably why they cost from $1,600 to $2,400 (or more for custom woods). The tines are tuned according to this fantastically complicated scheme. There's also some kind of MIDI controller, but I can't find out much about that from the site. (Thanks Carl)