The WiFi detector shirt from ThinkGeek finds WiFi connections and displays signal strength by lighting up the blue bars. Currently, the shirt is only capable of detecting 802.11b and 802.11g signals. It runs off of three AAA batteries and will set you back $30, but they're currently sold out. You know, I too have a clothing based detection system. Except it detects women's breasts. Whenever it detects a pair it makes my pants uncomfortable. Pretty amazing technology really.
Product Site [thanks again to the very handsome Derek for the tip]