The NetSpot Team has released NetSpot, free Wi-Fi mapping software for Mac OS X. It lets you run a Wi-Fi site survey and map wireless coverage of a living area, office space, new building, etc.
NetSpot Wi-Fi mapper lets you diagnose areas of poor reception in your Wi-Fi network, as well as locate troublesome areas of noise-generating machinery that could be causing wireless traffic issues. It’s compatible with Mac OS X 10.6 or higher. It’s available for download worldwide from the NetSPot App website (http://www.netspotapp.com).