Angry Can I check what data is transmitting out on Rooted Nexus 7 running kitkat

quick question, I have a bunch of rooted Android devices. On all my devices I have a meter that shows my upload and download speed. I recently just noticed on one of my devices, Google Nexus 7, that's running a custom ROM w (aokp)ith kiflat is always transmitting data on the flip side even if I just turn it on or in the middle of the night. I'm trying to figure out a way that I can monitor which app is transmitting data. Is there any specific app that will show me what is (app / process) sending data without my permisiion or knowledge. Is it possible to see what is being sent and to where?

Thanks in advanced.