I saw an Outbound in the early 90s if my memory is right. Their use of the tiny bar as mouse replacement looked really cool. Kinda want to play around with that as an input device.
I have one in the basement! The bar was called the "ISOpoint" bar. It was a great use of the tiny space. Also innovative was the IR keyboard. You could disconnect and move it pretty far from the main unit.
The Rollermouse Free product appears to be cut from the same cloth. The learning curve might be troublesome.