Kensington WiFi Finder
Living in a town where WiFi is still something of a rarity, it's a hassle to open my laptop and check for a signal in every building I visit. A WiFi detection tool attached to my key chain makes perfect sense. Kensington's device detects 802.11b and 802.11g networks within 200 feet, indicates signal strength, and filters out things like Bluetooth to eliminate noise. The only thing the WiFi finder lacks is an LCD with SSID and channel information, but for $15 signal detection goes a long way.