With this app you get a WiFi signal meter and measuring tool for the attenuation of walls.

With the signal meter you can see the current signal level your phone is receiving for an SSID. The signal can be shown for each visible antenna and frequency.

Furthermore this app supports you in measuring the signal loss of walls by doing reference measurements which can be reused for different types of walls. Please see the tutorial scetion in the app to get a full explanation of the process.