The studs I used were 10mm conical studs, which you can find easily and cheaply on eBay, and a few small triangular studs around the hole for the camera lens. I used pliers to fold the prongs inside them, then used a glue gun to stick them to a cheap clear phone case that I also got from eBay. I used 61 studs on my case and my phone is a HTC Desire (about the same size as an iPhone), which might be of some help if you decide to make your own.
It was a bit of a fiddly job and it's not turned out quite as neat as I'd have liked. It was quite difficult getting the right amount of glue into the back of the studs, (you have to fill the whole space inside them, it'd be too fiddly and not secure enough to glue around the edges) and because they're metal they conducted the heat of the hot glue, meaning I couldn't just hold them in my fingers and then stick them on. In the end I ended up sellotaping a cotton pad to the pad of my index finger, then putting more sellotape on sticky side up, to hold an unpside-down stud in place whilst I glued it, then used my big cumbersome sticky finger and the pliers to get the stud into the right position on the case. I'm sure there are far easier ways to do this though, and I'm just a bit of a dolt.
Still, for all the finger-burning and visible glue, I think it looks pretty cool, and it isn't uncomfortable to hold and use (a bit weighty though, but you could always use it as a weapon or window-smashing device in an emergency...)
What do you think? Also, If you haven't seen it already, check out my last DIY: wire-wrap hairbands.