Only few persons have the awareness and the knowledge to understand the effects their actions have on the environment. Not everyone is climatologist, economist, and marine biologist, but with digital technologies you can use the knowledge of those who are. Specifically, mobile phones are well suited to follow your way of life, they track how much you walk, cycle and drive. When you input what car you drive it can easily estimate your impact on CO2. When you shop online, your mobile phone can do the same for your merchanize. Done in the right way, this is not big brother watching you, it can make you aware of what your actions cause - and can help you make the right choices.