The Taiwanese creators of the Power Ball (United States Patent US5800311) and accessories such as:

the SM-01 (a speedometer),

the PBIO-01 (plugs into an ISA slot lets up to four Power Ball users compete - and it's GUI-fied, although only available for Windows.. I wonder when the Linux device drivers are coming out? although it don't really matter to me because a. I don't have one of these, and b. I run Windows 2000)

the PBIO-02 (sort of the same thing as the PBIO-02, but it plugs into the parallel port, and only supports two Power Balls..)