im looking for a tool...
 

...that will just keep track of the amount of data that has passed in and out of interfaces. similar to du meter for windows, but doesnt have to be graphical. it also doesnt have to tell me what the data was, just how much.

ifconfig seems to loose count :>#

ta

You possibly use an iptables firewall.
If so, then you can insert counting rules among the iptables firewall rules.
Then you can read out the counters say... once in each minute.

(At least I do this on FreeBSD: it is a very simple script of mine that keeps track of our internet traffic.)