Tracking carbon footprints by phone

A fascinating story in today's Guardian about an application that automatically tracks your movements via your mobile phone and uses the data to calculate your carbon footprint. Carbon Diem's inventor, Andreas Zachariah, a graduate student of the Royal College of Art in London and chief executive of the appealingly-named Carbon Hero company.

Carbon Diem is the world's first automated carbon calculator. It uses GPS to measure the speed and pattern of movement, using an algorithm to identify the mode of transport being used. It can therefore calculate the amount of carbon dioxide that a journey has emitted and keep a constantly updated diary of a person's carbon emissions, without any need for input from the traveller. As a result, a user can easily track their environmental impact and, if they choose, modify their behaviour to lower-carbon alternatives.

It's a great idea, but I wonder how it tells the difference between walking and crawling along in a traffic jam? And it may be difficult to track journeys made by tube when no signal is available underground. But anything which makes monitoring environmental impact easier for the user can only be a step forward.