GlassWire

If you have a very strict data plan on your mobile device, you might need an app that really good at keeping track so that you don’t get overcharged. In fact, this is really important if you don’t want to be spending money on extra GB each month.
The application is smart enough to be able to track separately the mobile and the Wi-fi data, which is a really important feature. It’s also possible to see what app is consuming the most data and to set up alerts for so that users know when they are approaching the limit.
Furthermore, it’s important to note that the application doesn’t store any kind of data regarding its users, making this one of the few in the Google Play store to do that.