iStumbler displays data about Wi-Fi connections available for you. It shows details for each connection found: name, strength level (graphical and number), noise, channel, frequency, band (GHz) and security status (open, WPA, WEP etc.).
This tool may be a good KissMac alternative that helps to check your WiFi quality and strength. Also, it can be useful to detect easily open connections in public places.
Other features includes scanning and data displaying for recent or current connected Bluetooth devices and view their properties.