Eton has managed to produce lots and lots of gadgets that were considered to be energy efficient and included solar power over the past years. Here is another one from Eton, the Rukus, which becomes the first portable Bluetooth sound system.
Rukus consists of a solar panel and streams the music from any compatible device wirelessly. Apart from being made to be portable in nature, the Rukus has some perfect speakers that are quite estimable too. This can help in producing some super noise.

The Controls
The Rukus has controls on the front side that includes the Bluetooth toggle, the Power button, and buttons for volume, bass and aux adjustments. The e-ink display of the Rukus Bluetooth sound system displays solar charge levels, battery levels and the Bluetooth status.
Solar Panel
The most magical part is the 40 square inch solar panel that can yield the energy from the sun. It actually takes 6 hours to absorb energy from the direct sunlight and get recharged. Eton has claimed that the Rukus will never run out of power.
However, you can take it the other way since that sounds to be too much of a claim. It can actually be charged using an AC adapter too and hence remains to be quite energy efficient in nature. The Rukus also consists of an incorporated USB port that helps to charge other devices.
E-Ink Display
The display part of the Rukus is said to exhibit details without making the battery to get drained in a small time period. The display consists of another advantage too. It can also be interpret in direct sunlight and even at a 180 degree angle view.
Price Range
The Rukus is said to be made available in Q2 2012 for a price of about $149.95.
