This is designed to help productivity since you can redefine keys to emit any useful sequence.
An example of such a keyboard is the Ortek MCK-142 Pro.
Here are a few places that sell it. (no, I don't work for these guys) -- RonPerrella
JerryPournelle had [nice things to say about them].
The Gateway computer's AnyKey keyboard (with 124 keys) is a popular one, still today. Search on eBay for one.
The Optimus keyboard is gorgeous! http://www.artlebedev.com/portfolio/optimus/
Avant Stellar is another one: http://www.cvtinc.com/products/keyboards/stellar.htm