USB Fever has released the Solar Power Pack the for iPhone 4G (http://www.usbfever.com/index_eproduct_view.php?products_id=1999). It’s an US$56.99 power pack with dual power sources: solar or USB mini five-pin.

With it, you can enjoy your movies, music, phone calls and internet surfing without worrying about the battery running out, according to the folks at USB Fever. This portable charger can recharge your iPhone to 100% about one and half times when the this powerpack is fully charged, they add.