iStumbler is the leading wireless discovery tool for OS X, providing tools for finding AirPort networks, Bluetooth devices, Bonjour services, and your GPS Location with your Mac.
iStumbler is $20 for all the computers that you own. Download iStumbler and try it out for free, then purchase a license within the app via PayPal or Coinbase. Previous donors and subscribers are entitled to a free license: see the store page for details.