Wardive is a neat use for your aftermarket DS flash cartridge that won't make Mario cry. A homebrew game, it uses the DS's Wi-Fi to scope out local hotspots. Then these hotspots become enemies in an ever-evolving battlefield (pending you move around a bit).
Your route to work can then become a map, with different levels of play (with varying difficulty) available just by walking a different way home. It's a simple idea that, who knows, might even be as fun as it is original. Has anyone tried it out?