I’ve been using the ZyXEL AG-225H WiFi Finder the last few months when I need to see if a hot spot is nearby. Overall I’ve been more than pleased with and like it more so than the Canary Wireless unit.
Why? It has 802.11 a, b and g, a much more descriptive display and it’s also smaller. The big benefit is you only need to attach it to a USB port and voila, it recharges, plus if you need to go A, it’s already there.