KisMAC is an application for Mac OS that scans networks to find all internet connections available. Is useful to detect quality WiFi connections prior to join them.
View hidden WiFi connections, view signal strength, view logged in users to a network where you have access.
Can be used successfully in airport and public places to detect the best connection and join it. Also, can check your home connection to view quality or to discover other connections that may interfere with your network.