I would get a cottontail rabbit distress call whether open read 9reccomended) or closed reed, and practice with it. They are very versitle, especially the open reads, with practice you can make all kinds of different distress sounds. There are lots of production calls in most hunting stores, but i think the "custom" calls made by call makers are THE best value and performance, and most of the time they are the same price or cheaper. if interested send me a PM and ill give you email addresses for some great call makers.
As to the IPhone aps, i dont know, but i would guess they are not very loud? I would invest in a Ecaller if you dont want to hand call, that way you would be handsfree to be ready with your bow for any takers.
The Foxpro spitfire is an economical well made call that holds plenty of sounds and would serve you well. The higher priced calls just have more features that may or may not be needed, that can only be determined by the user, personally i thinks some features are nice but not neccesary.
Good luck
Fin