inSSIDer - inSSIDer Essential makes it easy to maintain small business WiFi.
Wireless Network Watcher - scans your wireless network and displays the list of all computers and devices that are currently connected to your network.
NetSpot - NetSpot is a free app for wireless site surveys, Wi-Fi analysis, and troubleshooting
Homedale - With Homedale you can search for Wi-Fi / WLAN Access Points and monitor their signal strength.
Aircrack-ng - Aircrack-ng is an 802.
Kismet - Kismet is an 802.11 layer2 wireless network detector, sniffer, and intrusion detection system.