Just had a guy in my club blasting the iPhone on our forum because his wife talked him into getting one because it would do "everything" he needed in one device. He tried using it on a 100 mile ride and lost battery at mile 86 and, because of that, says that iPhones suck.

I told him, "I would not say such things if I were you."

I told him to use a bike computer for a bike computer and the iPhone for everything else on the planet. (My entire family of four has an iPhone each ... not to mention my brother, his wife, my sister, her husband, their daughter and son .... even my 3 and 4 year old niece and nephew have iPhones! They don't have phone service ... just use mom and dad's old iPhones for games. Pretty funny seeing a 3 year old totally iPhone savvy!)

The iPhone 4 has longer battery than the others, but still not sure it's the best option for a 100 mile ride. Guessing that's not what you need it for, but maybe the RunKeeper that CycleTherapy recommended will work for you. I don't typically use a navi while riding, unless I stop to check a turn so I'm not much help. Just love iPhones and had to share the discussion that's going on on my club forum. Hope you figure out a good option.