How can I tell what apps on my (android) phone are using bandwidth?

My usage for the last month is 3gb, and I have no idea how. My usage log on my verizon account shows stuff like 100mb data usage at 4:45am last friday when I was asleep. I know they are going to be capping bandwidth soon so I want to figure out what’s doing this and kill it.

There’s an app for that.

Thanks Murph - I had seen similar apps but they only tracked your phone’s overall usage, not by app. I installed that and will be curious to see what it reveals.