iPhone apps can only be compiled with Apple's Xcode which only runs on OS X. So the only way to compile an iPhone app on a Windows machine is to run OS X in an emulator. These only run on some windows machines and even then I have heard it does not work so well. So Mac mini is probably the cheapest way to get iPhone app making for Windows users.

also running OSX on a machine that is not from apple means terminating the apple's agreement i think. all engines need mac for building the game. even shiva3d that don't need a mac for development needs a mac for final build. in shiva you can not create real games easily because you can not test them in iphone and should use wiimote for getting input. so the only way is to buy a mac.

You can use Airplay SDK. Better than Unity 'cause it creates real native code - final product is not bloated. You can create useful software for iphone, ipad, ipod, Android samsung bada and of course symbian. Note: Android games created with unity cannot run on real phones because v7 of ARM is required which is available in only 0.1 percent of androis models. Airplay created adroid games and apps can run on all models