by Gregorius Glegar
Switches network mode to 3G preferred upon turning on the screen & unlocking device, and 2G only on turning off the screen after preset delay. Switch to 2G also occurs on connecting to WiFi. Delay are set using duration picker.
Also, I've added several constraints as to when the switch to 3G will happen, such as call state, battery level, and lock state. Edit these constraint blocks as preferred.
I found this saves quite some battery, especially if you live in places where 3G signals are unstable, thus eating up your battery even on standby.