The release of Nova Media's Traffic2Net brings relief to those Mac users who need to monitor just how much bandwidth they use while on a 3G connection. Traffic2Net watches the data flowing through your USB or ExpressCard cell modem, and shows you a running tally in the menu bar. Pop-up alarms can be set to warn you when you're hitting the ceiling of your current connection--or just blowing too much of your cell data mindlessly surfing Facebook.
Nearly every legitimate means of getting your MacBook online has a monthly cap on the amount of data you may download, and your Mac will happily blow past that limit by blithely downloading podcasts downloads, while you're sleeping. It's enough to remind some of us--the demographic that fondly remembers the original A-Team--of what it was like to go online in the Reagan administration. Back then, we paid by the hour of online time, an experience we were glad to forget.
iPhone users who were simultaneously granted kosher tethering from AT&T and a monthly cap on their data usage are temporarily out of luck; Nova Media is still testing iPhone tethering over USB and Bluetooth for accuracy, and expects to have an update out within a few weeks. In the meantime, check out either iStatMenus or MenuMeters, either of which will provide live and cumulative bandwidth statistics, but don't provide Traffic2Net's feature of maintaining those counts over a billing period.
Traffic2Net requires Mac OS X 10.5 or 10.6 and runs $15 for U.S. and Canadian residents, €15 for Europeans. A 30-day full trial version is available for download.