Actually I have a wireless 3G modem that works well on Windows based operating system, its interface software were made Windows centric. It can still connect to internet on Ubuntu or other linux based operating system but it won't show the data counter (the interface which shows how much data has been transferred, at what speed).
If I continue to surf internet in Linux then I won't have any idea how much data has been used and it would become heavy on my pocket. So I just want a software that let me know how much data has been transferred, if there is a limiter; that warns or disconnects me when I reach predefined MBs then its better. Please let me know if there is any software or script or something like that already there.
System Monitor
It is default in ubuntu ,you can see speed and data count in it :)
Nanny
A parental control tool for ubuntu .It needs more improvements ,but still works.It is available in software centre
Here is some usefull links: