Sniffing for Wi-Fi

I was reading my latest issue of PC Magazine and I ran across an article about a keychain sized device called the Wi-Fi Seeker that will sniff for Wi-Fi hot spots. I have a program on my Powerbook that will do the same thing, but this device just requires the push of a button and it will check for local hotspots. Now, it gives you strength on a scale of 1 to 4 little LED lights, but it beats getting out a PDA or Laptop just to check for a wireless access point.