Are you using PC or Mac?
I ask because you might be able to have the meter display "packet" usage. Similar to bandwidth... a program to display the packets sent and received. I have both; with the mac you can get a program called kisMAC trunk r239 to display all sorts of cool radio data (wifi). With the PC you might be able to use the standard internet connection program. Anyway, cool project and good luck.
BTW - I think it might be easier to write a page scraper for the internet based weather data or something... if all else fails.