WiFi Analyzer — Matt Hafner
inSSIDer - MetaGeek
A few tips on using inSSIDer to improve your WiFi configuration and get faster WiFi
NetSpot WiFi Site Survey Software: WiFi Heat Maps, Network Planning Tool. Free Plan.
NetSpot helps you plan wireless networks, create WiFi heat maps, run wireless site surveys & analyze Wi-Fi on Mac OS, Windows and Android, free versions available.
WiFiAnalyzer
Android application to analyze WiFi signals.