NetSpot is a simple and accessible wireless survey tool, which allows collection, visualization, and analysis of Wi-Fi data using any MacBook.
It can visualize your wireless network by building a visual Wi-Fi map, letting you see dead zones without coverage and place hotspots (access points) correctly. Using the visualized map of collected wireless data, you will also see channels' load, and will be able to decide how to optimize your Wi-Fi site.
NetSpot works extremely well on the latest OS X. Very good info collected for wireless networks, especially if you are a techie! The mapping feature is highly useful to show wireless coverage, or lack of it, to my clients.