auto control wifi
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.