A couple of us have picked up Belkin's Nostromo SpeedPad, first off to try out in Diablo II.

I found that, for me, I'd just as soon stick with the left hand on the regular keyboard, but my buddy's still driving the Nostromo after a month or so, now including in Dungeon Siege.

The Nostromo is a mini-keyboard to run under your left hand while the right drives the mouse. The heel of your hand rests on a pad to anchor it to the table top, and a cushion sits under the palm to support the hand while fingers and thumb reach the controls.

There are 10 keys in two rows of five under your finger tips, and I think it'd be lots better with two rows just 4 keys each, since with 5 you have to pay attention to registering your fingers over the correct four-out-of-five. There's a speed-control wheel under your index finger.

The best feature, though perhaps trickiest to control, is the 8-way rocker switch under your thumb, which can be configured as a shifter for the finger-tip keys. Two lamps indicate what shifts are in effect: none on, red on, green on, both on. That yields up to 40 button definitions, assuming you can keep track of 'em all in your head.

There's a Nostromo Control application (for OS X) which handles all the configuration interfacing.

Works fine in OS X.