My company, 3rdwhale.com, just launched the beta version of a location based service for iPhones that allows people to be green on the go by leveraging iPhone's GPS and capabilities to find anything you'd like to do in a city in a greener way (eat, adventure, hotels, etc.). We have more than 50 cities in our database right now. We are however only doing an Ad-Hoc distribution through Apple so we can only take in 100 beta users right now.  If you are interested please check outhttp://www.3rdwhale.com/luna to learn more or to sign up.