Firstly, you need the Unity publishing license (See the Unity store)
However, due to the security restrictions of iOS, you'd also have to get a developer license anyhow (at $100 a year) to be able to legally put it on any phone. Otherwise, you'd likely have to jailbreak your phone after the application has been built (using Unity).
HOWEVER, there is an iOS app called the Unity Remote that lets you play your unity game from your computer over the wireless, but there's a good chance that won't suit your needs. It's still worth taking a look at, though, as it's a great tool to have.
Best of luck!
answered Sep 08 '12 at 02:55 PM