Oh man I totally need to get me one of these! BoingBoing posted yesterday about a DIY project that can give you a “sixth sense for wireless networks.” Here’s the project description:
This project is for a small electronic unit that allows the user to sense the presence and relative signal strength of wireless hotspots. It can be worn as a pendant or carried in a pocket. It is “always on” and communicates the presence and signal strength of an in-range hotspot by way of sequences of pulses – like a heartbeat you can feel. The stronger and faster the “heartbeat”, the stronger the wireless signal detected.
Just imagine walking around a city’s downtown with this thing on…it would never stop pulsing! Very cool idea though.
Read: BoingBoing
MasterMaq's Blog 
My new Dell Notebook has this built in. It’s basically a Wifi Sniffer.
Sure, wi-fi finders have existed for a while…but this is the first one I’ve seen that vibrates!