also, vnstat: http://humdi.net/vnstat/
$ vnstat Database updated: Mon Apr 16 23:30:11 2012
eth0 since 02/01/12
rx: 3.54 TiB tx: 21.11 TiB total: 24.65 TiB
monthly rx | tx | total | avg. rate ------------------------+-------------+-------------+--------------- Mar '12 1.78 TiB | 9.99 TiB | 11.77 TiB | 37.74 Mbit/s Apr '12 1.14 TiB | 7.07 TiB | 8.21 TiB | 51.06 Mbit/s ------------------------+-------------+-------------+--------------- estimated 2.14 TiB | 13.27 TiB | 15.41 TiB |
daily rx | tx | total | avg. rate ------------------------+-------------+-------------+--------------- yesterday 32.98 GiB | 399.86 GiB | 432.84 GiB | 42.02 Mbit/s today 19.55 GiB | 274.59 GiB | 294.13 GiB | 29.16 Mbit/s ------------------------+-------------+-------------+--------------- estimated 19.96 GiB | 280.43 GiB | 300.39 GiB |
edit: Things I like about vnstat,
I don't use Shaw, as they don't provide internet access in my area. But I did grow concerned about things like this a few months ago. Not necessarily no usage monitoring, but I had heard horror stories about certain large providers who didn't even have the capability to accurately monitor these things, yet still charged for nonexistent overages.
I already had a Linux box with multiple NICs acting as a router, so I threw vnstat on there. It seems to work fairly well, and I trust it far more than whatever numbers my ISP might throw at me.
vnstat is pretty basic but easy as hell to set up. It won't give you exact numbers but they'll be pretty close (along with extrapolated estimates for monthly usage, etc.).
Also a huge feature for me would be able to have something like vnstat (http://humdi.net/vnstat/) built into Plex so that I can see how much bandwidth is used on a daily/weekly/monthly scale per client/network. But I also paid monthly for Plex for many months then finally went to Plexpass lifetime to support the project all in hopes that they will add all these features, every dollar helps a project mature.
Like xixel was saying you can install a 3rd party firmware if your router supports it. It's a little bit technical though so it might not be for you. It is really the only way to track usage for every device connected to the router.
I use the OpenWrt firmware on my router and vnStat to track my usage.