The problem with using mobile phone headsets is that some of them are good enough only for a specific number of hours. But that would depend on where they get their source of power. As far as SolarVOice 908 released by i.Tech Dynamic, soliciting its energy from solar power makes it technically an infinite powered Bluetooth headset device add-on.
The SolarVoice weighs only 13.5g and features a built-in solar panel that harnesses solar energy whenever the panel faces the sun. A complete recharge is done through 15 hours of sunlight that in turn offers 5 hours of talk time. However, charging from a USB port or via AC mains when using the device for the first time is still recommended. The SolarVoice 908 retails for about $73 and will become available by September 10.
(Source) Eco Friend