Don't forget that all devs should have to shell out $s to get iPhones and iPods.
that's clear. although i suppose that some preliminar work can be done with the emulator that apple provides.
Also, how the hell can you play with one big touchpad?
two possible solutions.
1) the speedometer (not sure on the original english name of the thing): it will play like a game on the wii. difficult to master, but could be very fast once you're used to.
2) a virtual keyboard. quake 2 is playable that way inside the playstation emulator.
For example the game could be played portrait mode with a left section of the screen with virtual controls for forward, backward, strafes, jump and duck, a right, bigger, one for viewing the game and looking around with your finger(s) and a small bar in the lowest part of the screen for triggering the fire button with your thumbs.
The interface itself is the problem: not thinking of an usable interface (there are lots of possible configs) but coding it. Unless ioq3 for iphone/itouch comes out from someone with commercial intentions it's probable that it will come out very soon...without an usable interface (that will come later).