Years ago (early 80's) one of my Dad's buddies was a dealer for the Writehander.

http://research.microsoft.com/en-us/um/people/bibuxton/buxto...

It never really took off, but at the time, it was super cool.

Edit: some more links on chord keyboards:

http://www.billbuxton.com/input06.ChordKeyboards.pdf

http://www.dougengelbart.org/pubs/augment-14851.html