Network Signal Info" provides detailed information over the currently used network, whether WiFi or cellular connection.
Two widgets, one for mobile- and one for WiFi-signalstrength.
(If you can't find widgets, please copy the app to phone memory)
I have put special value on the visualization of the WiFi and mobile signal strength. They are normally only divided in weakly, good and excellent. Graphically in the form of mostly "only" three to five bars on the Mobile Radio and three to five "waves" by a WiFi connection.