inSSIDer allows you to scan the Wi-Fi networks around you and track their signal strength over time. inSSIDer scans all the Wi-Fi networks within the reach of your computer’s wireless card, tracks their signal strength over time, and determines their security settings. You can track open or secure wireless networks, or determine the best channel for your own wireless network.
This app is no longer available from either the MAS or from MetaGeeks, LLC.
The new site, inSSIDer, from which v4.0 for OS X is available for $19.95, is at
http://www.inssider.com/