An enterprising hacker, noticing that his Nokia 6230i mobile phone has both an imaging sensor and Bluetooth, much like a wireless mouse, has
written a Java applet that uses the phone as a mouse. It's not perfect (the imaging sensor is not designed for focussing so closely, so it needs a high-contrast surface), and currently requires a special custom driver on the computer, though he is working on making it behave like a standard Bluetooth mouse.
The hacker, going by the name of "Pyrofer", also has a number of other projects up, including a 1541-emulating memory card reader for the C64 DTV.