I have a Droid phone and I know NOTHING about iPhones. That being said...I use a micro SD card in a full size adapter in some cameras so I can just read the micro SD card directly from my phone.
Yes. Apple sells an SD card reader that plugs directly into your iphone. My friend has one that he checks his cams with. He bought his at Bestbuy I think. You don't have to jailbreak anything.
The one that works on the ipad doesn't work with the i4 (it plugs in, but doesn't work -- tried it with two seperate readers). Let me know's for sure if it works on the i5. About to upgrade and that would be a lot less bulky than carrying an ipad into the woods.