After unending frustration calibrating an FTIR multitouch device Eric and I decided to take a different tack for a navigation game we were building. We took his giant circus ball and mounted it on casters, then pushed an optical mouse up against the bottom of it and voila! a giant trackball. So simple, but the increased size makes navigating gigapixel images much more fun than sitting at your computer. We paired the device with a few jumbo Happ Control buttons and a large projection to let players navigate around huge images. Thanks to the folks at Gigapan for use of some of their super high quality images!
YouTube video