Brazilian company HandCase is distributing free downloadable software for keeping track of your CO2 emissions and to purchase carbon offsets on your Palm OS mobile devices. C02 Global enables you to estimate your emissions, and to manage the certificates that you purchase.

Judging from the press release and the website, Handcase is much more comfortable writing in Portuguese than in English, but versions of the software have popped up on many download sites. I'm sure Handcase won't be the last company to look at tracking C02 emissions on a mobile platform.