I know it would definitely be hard, but perhaps an iPod Touch's accelerometer could be used to control a mouse similar to that of Touchpad Pro, which is VNC based. The iPod Touch could be pointed at marked spots on a big computer screen- which would have to be relatively large for any sort of accuracy (I was thinking flat screen TVs hooked up a computer)- and then the accelerometer would be logged with these points, which could be used to calibrate the iPod. With this information, the movement of the accelerometer would then move the mouse. Tons of calibration would be required (distance and screen size must be entered) and a client for the computer would have to be created, or paired up with VNC. Even though this seems difficult, I feel this would not only be an interesting feature, but could be developed further and utilized in games.