If you want to develop an Android app to turn on/off GPS you can use the following code snippets.

// turn on gps
public void turnGPSOn()
{
     Intent intent = new Intent("android.location.GPS_ENABLED_CHANGE");
     intent.putExtra("enabled", true);
     this.ctx.sendBroadcast(intent);

    String provider = Settings.Secure.getString(ctx.getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
    if(!provider.contains("gps")){ //if gps is disabled
        final Intent poke = new Intent();
        poke.setClassName("com.android.settings", "com.android.settings.widget.SettingsAppWidgetProvider"); 
        poke.addCategory(Intent.CATEGORY_ALTERNATIVE);
        poke.setData(Uri.parse("3")); 
        this.ctx.sendBroadcast(poke);


    }
}

// turn off gps
public void turnGPSOff()
{
    String provider = Settings.Secure.getString(ctx.getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
    if(provider.contains("gps")){ //if gps is enabled
        final Intent poke = new Intent();
        poke.setClassName("com.android.settings", "com.android.settings.widget.SettingsAppWidgetProvider");
        poke.addCategory(Intent.CATEGORY_ALTERNATIVE);
        poke.setData(Uri.parse("3")); 
        this.ctx.sendBroadcast(poke);
    }
}

Source:
http://stackoverflow.com/questions/15426144/turning-on-and-off-gps-programmatically-in-android-4-0-and-above