no. if it's unlocked you are effectively buying it sim-free. I would just stick a cheap SIM in it like the one from China, or the $10 t-mobile prepaid sim in the US if you need to do it to activate it. Or the one in your current phone.

Though if you are doing this for ipod + camera, and you will never use the phone part of it, I would consider just buying an ipod touch if you want/need the ability to run ios apps and a separate camera. standalone cameras are still much better than any phone camera, regardless of their resolution ratings. (the sensors are tiny on phones.) I can get some decent pics on my iphone 4, but none of them are close to the quality level I get from a standalone camera with a nice lens + sensor. For example, the Canon S95 or S100 is going to be much better than any phone camera, and it will still fit in your pocket.

Regardless of that, as long as you buy a factory unlocked iphone, your plan will work.

-David