A new mobile application uses your phone's built-in GPS to sense whether you're travelling by foot, bike, car or train, and calculates your carbon footprint in real time.

The Carbon Diem application has been tested in (unnamed) Nokia and BlackBerry phones, where it managed to guess that it was travelling on a bus around 70% of the time, according to a feature in The Guardian.

When travelling by plane or train, its accuracy soared to "nearly 100%", according to developer Andreas Zachariah of UK start-up Carbon Hero. Zachariah went on to suggest that companies seeking to reduce their environmental impact might want to track their employee's travel habits.

Carbon Diem, which is due for a commercial launch next year, has already won a string of sat nav and green awards.

Fiddling while the planet burns

Here at TechRadar, though, we reckon it's a prime example of 'green bleat' - a completely unnecessary product that stokes the smugness of 'greener than thou' eco-hipsters while doing nothing to actually address the issues of climate change.

Everyone already knows that walking and cycling are cheaper and more eco-friendly than car or plane travel. And even if they didn't, what is Carbon Diem suggesting, that people who remain completely stationary are somehow better than those who move?

And that's even before we address the privacy issues of a company tracking its employee's travel, or the additional CO2 emitted by leaving a mobile's GPS unit activated 24 hours a day (you'd need at least a couple of extra batteries and chargers).