Griffin's PowerMate Bluetooth is a shiny spinner knob. You hook it up to your computer via Bluetooth. Then you can control something with the knob. Volume sliders, browser scrolling, Arkanoid, whatever—just so long as it's on a Mac. So you can't really control anything, per se, and it is not "unlimited," as suggested in the marketing copy. In addition to computers running the Microsoft Windows and Linux operating systems, your destiny cannot be controlled using the PowerMate Bluetooth.
But for those with a Mac, there's an included app to program more complex scripting around the gadget, too. One AAA battery provides two months of use, according to the specs. It's $59 from Amazon.