The trend towards environmentally-friendly mobile phones has turned to better forms of energy usage.

Last year, many mobile firms fought to create the best devices using recyclable materials, and now the race has switched to energy efficiency. Last week's Mobile World Congress saw Caribbean manufacturer Digicel reveal its low cost Coral-200-Solar, an entirely solar powered handset that has a greatly reduced impact on the environment.

Following the small company's lead, global giant Samsung also hopped on the solar power bandwagon by showing off its similarly-run Blue Earth device. Constructed from recycled plastic and recharged via natural resources, the Samsung Blue Earth's environmental message comes across even in the software package it totes.

An eco-mode button sets the brightness of the screen, Bluetooth and the backlight duration at lower values in order to conserve battery. The phone - shaped to look like a flat and shiny pebble - even includes a pedometer that compares steps taken with how much CO2 emissions would have been discharged into the environment had the owner used a car or other form of motor transportation.

Mobile World Congress saw many other innovative and original ideas from the world's top mobile phone companies. Nokia revealed its own Nokia Apps Store, a rival for Microsoft's Windows Mobile, and a possible competitor for Apple's iPhone apps store.

LG bucked expectations with the unveiling of its wristwatch phone, a touchscreen device the user wears strapped to the wrist which doubles as a watch. Motorola also made a promising appearance by revealing its plans to work closely with Google Android in the future, with its first Android-run phone expected to appear next month.