A free program for Android, by StickyApple.com.
WiFi Auto Reconnect is a handy utility that can automatically reconnect your device to Wi-Fi when it goes offline. The app is useful when you need to stay connected to the Internet even when your device is in a bad connection or you are using a mobile data connection with a low bandwidth.
When you're connected to Wi-Fi and lose your Internet connection, it will automatically try to reconnect to the saved Wi-Fi network you have configured. The app can run in the background to ensure that it will continue to try to reconnect even when the app is not in use.