Triplett WiFi Hound 2.4 GHz and 5 GHz Wireless Network/RF Spectrum Analyzer to Visualize and Troubleshoot Wi-Fi Issues for Smart Homes, Businesses, and More (WFHOUND): Amazon.com: Industrial & Scientific
8 Free WiFi Signal Strength Analyzer - Scan Neighbour's WiFi To Avoid Channel Conflict
RF Viewer — Low-Cost, Wireless USB Dongle, RF Spectrum Analyzer
TOP 5] Best WiFi Analyzer Apps for Mac OS (Free and Paid)