Network Monitor

[SpykeZ]

Simple and Statistical precision.
Support a variety of Android mobile devices.

2G/3G and Wi-Fi network data traffic monitoring capabilities.
Network data traffic to warn function.
Real time monitoring of network data charts and summary.

Paid version：No ads.

I found this last night and found it to be very well done, it's simple and straight to the point. For people on limited data plans you can set up alarms to go off when your reaching a limit you put in.