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
Find Wi-Fi networks, Bonjour services or Bluetooth devices in your area.
WiFi Explorer will scan, find, and troubleshoot wireless networks.
coconutWiFi displays you a small aqua-bubble at the top of your screen which indicates whether you're in range of a wireless network or not....
App that allows you to control iTunes from a mobile device.
Crack any wireless network with WEP security.
View wireless signal strength connection in your menu bar.