The upcoming Rock Band 3 games' Keyboard Controller was recently approved by the FCC.
The controller can be worn with a strap, like the guitar controller. Has a MIDI Out port, and the USB dongle comes with 2 extra ports for your other instruments. It runs on 3 AA batteries.
FCC ID's P25M796161Y2310R P25M796161Y2310C P25M798161Y2310C