Here comes a test of using the Google Chart APIs to display dynamically updating data on this page. Hopefully, if I've done this correctly, as I track my data usage in a google spreadsheet, these charts should stay up to date over the coming weeks.
I'm still looking at the API to see what can and can't be customized. This is obviously not as powerful as some commercial tools, but it is a good start.
Below, you can see where I tested the speed of the SIM and it's ability to stream by watching youtube and using skype. If I would have continued consuming data at that pace, I'd have used the full charge in about a month.
This graph allows zooming in on different dates. The flat part of the graph is goldenweek.