NetSpot is a software tool for Wireless networks assessment, scanning and surveys, analyzing Wi-Fi coverage and performance. It runs on Mac OS X 10.6+ and supports 802.11n, 802.11a, 802.11b, and 802.11g wireless networks. NetSpot uses the standard Wi-Fi network adapter and its Airport interface to map radio signal strength and other wireless network parameters and build reports on top of that. NetSpot was released in August, 2011  and now available at MacApp Store.
NetSpot provides all professional Wi-Fi site surveys features and maps Wi-Fi coverage of a living area, office space, buildings, etc. It provides visual data to help analyze radio signal leakages, discover noise sources, map channel usage, optimize Access Points locations. Additionally, the application is capable of performing Wi-Fi network planning: the data that are collected help to select channels and placements for new Wi-Fi hotspots. NetSpot can generate survey reports in PDF format.