I took some time this past weekend to play with my Pebble and ended up coding a small JS watch application to show me the current usage on my TekSavvy connection.
I present: "TekSavvy Usage".
It's a simple app that will show you how much bandwith you've used along with how much is actually counted. As I don't have a way of telling what type of connection (Cable/DSL/etc...) along with the actual cap, I've kept it simple to show what's been used both on (counted) and off (not counted) peak hours (2am to 8am is off peak).
Press the select button to refrest the information. The data seems to be refreshed once per day.
A small note, I am not at all affiliated with TekSavvy (except that I use them as an ISP) so this app is not supported or endorsed by them. Thanks to Andre for giving me the go-ahead to publish this.