We’ve seen a few on the go battery charging solutions for the iPhone and iPod Touch in the past and the need for those is becoming less and less due to better and better battery life in each new iDevice. So the way I see it is the on the go battery that will last out amongst the consumer has to be the cases with inbuilt batteries. Some may like the battery packs for travel purposes but for the average day person this is the only real purchase they will consider.