Here is a 3-in-1 external battery pack that adds DUAL SIM function to the iPhone 3G/3GS. The battery pack includes the Q-Dual Dual SIM card adapter that allows your iPhone 3G/3GS to use two SIMs. Users can easily switch between the two SIMs on the iPhone.
Other than adding second SIM to the phone, the device also serves as iPhone external battery with 1900mAh capacity and as a protection case. The pack/case allows access to all ports of the iPhone 3G/3GS so users can connect the iPhone 3G/3GS without taking off the battery pack.
This Dual SIM battery pack is priced at $59.99.