there is no way without a mac and a membership in the apple developer programm. The membership costs 99$(79€) per year.
The iPhone SDK with all tools is free and really great to use. The cheapest engine for the iPhone is probably shiva. It also renders quite fast on the iPhone since the last update. The disadvantage is, that the scripting is really hard, as you have to do a lot on your own.
I have no experience with Unity and Torque. But Torque seemes to be quite expensive for iPhone developement.