Renting a car can be a complete pain in the behind sometimes. Besides the price, the process itself can often be convoluted, requiring you to pre-book online or call in your reservation, and then you have to fill out all the paperwork when you get there. These days, renting a car is as easy as pulling your iPhone out of your pocket, and some of these apps promise you a better deal and a booking process that is much less painful than those of yesteryear. So, which ones are the best car rental apps for iPhone? Read on.