Es gibt also auch WiFi Detektoren:
„The credit card-sized WFS-1 can sense the presence of both 802.11b and 802.11g networks, and has an operating range of 500 feet outdoors and 150 feet indoors.“
Smart ID: WiFi Detector (WFS-1)
Gizmodo: SmartID’s WiFi Detector works
Gizmodo: SMART ID’s WiFi detector
Gizmodo: WiFi Finder
Gizmodo: WiFisense: wearable WiFi detector
Gizmodo: Down on Kensington’s WiFi Finder