WiFi Scanner for Mac OS X
WiFi Scanner is a 802.11 wireless scanner and connection manager for Mac OS X. This app will detect access points and clients in ad-hoc mode if the SSID is being broadcasted. It can be used for wireless site surveys, wireless discovery, and to connect to wifi networks. The tool reports signal strength in dBm and shows access point BSSID/MAC addresses.
Please see video below demoing WiFi Scanner v1.2 for Mac OS X.