Help finding an iPhone Case!

For the iPhone 3G, what is the best case that also has a battery on it..?

I know there are Mophie's that are like $80 and above, but I'm also interested in cheaper options. I see some on eBay, but I want trusted brands or trusted eBay products, so what do you guys recommend?

You can recommend battery cases or "battery backups" that aren't a case. Looking for less than $50, if possible, but will get me through a day without a problem.


2.

I am also looking for an iPhone 3G case that can be used with an ID card.. I see the Case-Mate 3GS ID case, but I'm also looking for other options. I'm not looking for one of those leather "flip" cases that have a pouch for the ID.

 

Anyone.