This simple app can help you increase the standby time of your device: WiFi Automatic automatically disable your WiFi radio when you don't need it and thereby lowers the battery consumption.
You can also specify to automatically turn on WiFi again, if you turn on your device or when you enter a specified location (requires a cell radio and therefore does not work on WiFi-only tablets!). Also, the app can regularly scan for available networks to connect to and re-disable WiFi if no suitable network is found. This way, you are always connected to your WiFi network when using the device.
WiFi Automatic is open source: https://github.com/j4velin/WiFi-Automatic
A WiFi connection generally uses less power than a mobile data connection, so on your phone, it makes sense to keep the WiFi radio active, whenever a WiFi network is in range
RECEIVE_BOOT_COMPLETED - is required to start the service again when rebooting your device
The following permissions are required to observe and change the WiFi state:
The following permissions are required to the "turn on WiFi when entering these locations" feature:
1.6.2: SCREEN_OFF timer was not started when WiFi was turned on while the display was off and no known network was within range
1.6.1: fixed issue where ON/OFF timers were not set again after first execution
1.6: added "active location scan" option for users having issues with the location feature
1.5.8: fixed issue with "turn WiFi off at" timer set to the wrong date in some cases
1.5.7: fixed crash on Android 2.3
1.5.6: added WiFi status information in the app