5. CollecTic - Interactive PSP GameThough not really a mod, this homebrew game is quite interesting none the less. Jonas Hielscher has developed an interactive PSP game called "CollecTic", which basically "has you running around outside trying to collect WLAN access points with your portable".
Each point is given a distinct color, geometric shape and sound based on its particular MAC address. The size of the point is determined by how strong the signal is. The object of the game is to fill your three-by-three grid with shapes, finishing with three in a row[Source]
4. Nintendo DS Lite CameraIf you're tired of waiting for Nintendo to come out with a camera attachment, then why not make your own? Here are the detailed instructions (w/software).
...apparently he's taken a Treva CMOS chipset, done a bit of rewiring, and written software that allows the unit to output images directly to his DS Lite[Source]