Stable WiFi automatically disconnects you from out-of-range WiFi networks
When moving around while connected to WiFi, many Android phones frequently "hang on" to a WiFi signal for far too long, even when you are out of range and are unable to actually transmit any data.
Stable WiFi allows you to set a threshold for your WiFi signal strength. When the WiFi signal drops under this threshold, your WiFi radio is temporarily disabled for a configurable amount of time, which allows your phone to fail over to a cell data connection.