Thousands of wireless networks beam the Internet across American cities, but finding a Wi-Fi "hot spot" can be a hit-and-miss affair, one that means repeatedly booting a laptop to find a signal. Now a variety of cheap and pocket-size Wi-Fi finders can help in the hunt, with lights that glow when an access point is near. It's a modern take on the ancient divining rod, whose supposed magical powers showed where to dig for water.

The smallest we've seen is the WiFi Seeker (wifiseeker.com) from Chrysalis Development. Push the WiFi Seeker's only button, and a light sweeps back and forth across four bars like a miniature radar set, stopping only when a Wi-Fi signal is detected. More lights glow or dim as you move closer to or farther from a Wi-Fi hot spot. That also makes it handy for pinpointing the best location in a house for a base station.

The WiFi Seeker, like competitors, is priced at around $30. Kensington was early to the market with its WiFi Finder (kensington.com), which is larger at the size of a credit card--and whose lights don't dynamically shift with signal strength. The WiFi Detector from Smart ID (smartid.com.sg) is also credit-card size, though with lights that readily shift with signal strength.

Each of them can tell the difference between a Wi-Fi network and cordless phones or microwave ovens, which operate in the same radio spectrum. The devices detect two Wi-Fi species, those based on the "b" (as in 802.11b) specification or the faster "g" hot spots. But none of the detectors will tell you if a network is open for public surfing or closed with tight security. There's only so much a few lights can say. (Software can help: TechBits has tips)