I saw this in Cool Tools and thought I would share

Canary Digital Wireless Hotspotter

Best Wi-Fi hotspot finder

Canary's hot spot finder is the best of the several stand-alone
Wi-Fi detectors that I've tried -- three of which I've gone so far as
to purchase. The Canary uses AAA batteries, rather than the button
cells that some detectors do (harder to replace in a pinch);
consequently it's not quite as svelte as some, but the extra goodies
are worth the chubbier, still-palmable housing. Canary's unit scrolls
across its 12-character LCD display the name, channel and signal
strength (4 bars is the highest) of the networks it finds, which makes
it truly useful for checking where your own access point's signal
reaches.