I was reminded of this by the recent post about "the Keyset". I read a review of one of these devices in a magazine ("Interface Age?" Byte?) back in the early days of microcomputers. It was a keyboard replacement that allowed the user to enter any ASCII code using binary chords. It had a button for each finger and eight for the thumb; if I remember correctly, the thumb buttons were effectively rocker switches. Set the four high bits with the thumb switches, enter characters via the four low bits entered with the finger buttons.
Somehow it didn't catch on.