Personal transportation is considered as the greatest contributor of CO<sub>2</sub> emissions in the entire world. Since transportation is a mobile activity, mobile devices are well suited to sense and provide feedback about these activities. In this paper, we explore the use of personal mobile phones to give users feedback about their carbon footprint due to different transportation choices and activates. We propose a mobile GPS application, <i>EcoDrive</i>, for iPhone that suggests the fuel efficient route to the user. It can inform user about alternative public transportation to the same destination. EcoDrive supports awareness of personal transportation activities, reminds users of additional reasons for being green (<i>e.g</i>., financial savings), and emphasize them to adopt eco-friendly behavior. The key contribution of this paper is the presentation of the design, implementation, and validation of the prototype of EcoDrive.