So I took a chance and purchased one of the i900 extended batteries (3000mAH) for my US Omnia (i910). As expected upon installing the battery, I received the standard message "Non Supported Battery! See User Manual." Searched and searched for a way to charge the battery while installed in the phone. I figured there would be a registry hack or other way to charge the battery. Obviously no such luck.

Finally started looking at the dock/external chargers. There is a model that will charge your phone and a second battery. After finding one for a good price, less than $40 shipped, I placed the order. Upon arrival, I set it up and eagerly placed the i900 extended battery in the additional battery charging station. It worked without any issues and I now have an extended battery that works great with my Omnia.

Obviously there are shortcomings with this setup as I have to take the external dock with me if I need to charge the external battery. However, I was out of town this last weekend and the phone ran a full 48 hours with the extended battery. Used the GPS quite a bit, streamed music over bluetooth and placed only a few calls. So, if you are looking for a way to use the extended battery, there you go.