I have tried this app on a phone I'm currently working on, and since that phone is rooted I checked with Network Log whether internet access was really blocked or not for the selected apps.
Well, I'm affraid that the app doesn't work, it can't prevent system apps from connecting to the internet.
The android system, the settings, the settings storage, the bluetooth, the finger print, the finger print app lock, fused location, key chain, the thermal manager, the sensor calibration and a few others (about a dozen in total), can all freely send and receive data.
On a fully stock rom there would be many more, if there are only a dozen or so on mine it's because I've already toroughly skinned the rom and uninstalled lots of system apps.
The thing is that those system apps can't be uninstalled or modified on a non rooted phone, unlike third part installed apps that only require a bit of reverse engineering to have their internet permission removed and can be reinstalled once modified, and I'm sorry to say so but that makes net guard of not very much use, if any at all since it prevents the user to use the VPN.
Nice endeavour anyway, 2 thumbs up to the great devs m66b and pluser_k2...:silly: