Handsets comprising plant-based plastics, 100 per cent recycled steel and a wearable strap made from solar cells could be the way forward for environmentally concerned mobile phone users.

The 'Eco Sensor Concept', dreamt up by researchers at mobile phone manufacturer Nokia, consists of two parts. A wearable sensor unit made up of solar cells analyses local environment, health, and weather conditions and is worn on a wrist or neck strap. Near field communication technology (NFC) then relays information from the sensor to a dedicated NFC-compatible mobile phone.

Users can choose which energy-saving sensors they want inside the sensing device, customising the handset according to their personal tastes. According to Nokia researchers, fitness enthusiasts could opt for a "personal trainee" handset, offering users an on board heart-rate monitor and motion detector (for measuring walking pace).

Nokia is hoping its 'Eco Sensor Concept' will help "stimulate an ongoing discussion and idea sharing – both within the mobile industry and with consumers”.