How can I monitor the network connection status in Android?

Listen for CONNECTIVITY_ACTION

This looks like good sample code. Here is a snippet:

BroadcastReceiver networkStateReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.w("Network Listener", "Network Type Changed");
    }
};

IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);        
registerReceiver(networkStateReceiver, filter);