What’s cooler than an iPhone case that recharges your battery? How about an iPhone case that recharges your iPhone’s battery with the sun.

Etón has released the Mobius NSP300B Rechargeable Battery Case for the iPhone 4. Featuring a 1800 mAh rechargeable lithium ion battery, the NSP300B sports a solar pack that will charge your iPhone with the energy it draws from sunlight.

Originally previewed at CES, Etón’s latest creation is definitely unique. The case itself actually looks pretty good. It weighs in at 3.4 ounces and includes a Micro USB cable.

The power pack features a fancy LED indicator that displays the amount of charge that’s been collected on the solar panel. There’s a stand by switch that allows you to collect solar energy without actually drawing from the case’s charge.

Etón claims that its case will give 25 minutes of talk time, 20 minutes of 3G data usage, 35 minutes of video playback, or 145 minutes of audio playback on one hour of solar charge. A fully charged case will provide 5 hours of talk time, 8 hours of 3G data usage and video playback, or 32 hours of audio playback.

You can pick up the Mobius NSP300B for $78 on Amazon.

What do you think of this particular case? Useful? Or do you prefer the darkness?