This device is comprised of:
1) Gloves with switches on the fingertips that have the same feel as a piano key
2) Low-cost ultrasonic tracker with two receivers (attached to each glove)
3) A main sound unit composed of a speaker with built-in amp and synthesizer & necessary electronics
Full-size cardboard printout of piano keys
The transmitter of the ultrasonic tracker is placed at the indicated location to the left of the "keys" The signals from the gloves are transmitted to the main sound unit. The main sound unit uses the distance of each hand from the transmitter and which fingers are being "pressed" to figure out which "key" has been pressed and how strongly. The sound is produced by the main unit. (This is essentially a compact organ with an alternate input device).
The gloves could have optical sensors to figure out which "key" they are on.
Multiple keypads could be created.
Keypads could be placed in weird locations for multimedia/performing arts kind of shows.