Please see the article in Business Week -
http://www.businessweek.com/technology/content/jun2009/tc2009061_692661.htm?link_position=link1
The US Corporations have begun tracking their carbon footprint with
spreadsheets and have come to realize what the impact is for them if/
when the "cap-and-trade" law becomes effective. (The large
corporations account for about 6% of the CO2 pollution today.) What
everyone has is just a rudimentary way of tracking the footprint one
time today. What would be ideal (as an opportunity for an
entrepreneur) is to pick up the information in real time and be able
to manage the carbon footprint in real time.
-anil