After reading this article How To Turn Your iPod Touch Into a Mobile Interview Kit [Macworld 2011] on Cult of Mac looks like you can easily hook up a mic that's not designed to use with the iphone or ipod touch.
I'm really enjoying my iphone 4 as a way to create on a portable basis. The camera is a fairly good quality and it has numerous apps to adjust and change images and video.
The only problem with the article and the original post is that a couple of links are not directing me to the product and also you could also use a different type of Mic.
My setup would contain
1. iPhone 1/8 inch microphone and headphone adapter - 3.5mm 4 conductor TRRS Male to 3.5mm TRS Jacks
I would use this to connect my 3.5mm male to 3-pin XLR Microphone cable, which from there I would connect my Rode M3. I've got a couple of other mic's that have a 3.5mm male jac so this would be more suitable to myself.
2. NAJA King Form
This Naja King Form is a great suggestion as it can move into plenty of positions and the form would allow me to fit it with a case on my iphone (like a case that has a battery for extra power).