I have an iphone. I use "map my fitness" which will record your distance and time. You can spend $.99 and get the upgrade, which will give you splits on the website as well. The app does drain battery life.
A GPS is handy and gives more accurate information.
I know there's another rider on here that had a really cool trail mapping app that she likes. You can even play your track back to you and a marker moves along at a speed relative to how fast you were moving, I.e. Faster when you were going fast and slower when you were going slow. It wouldn't work for me because I don't get service where I ride. However, if you're getting into endurance, I would really suggest getting a GPS - not only can you track for conditioning, but they're very useful on rides. Knowing how far I've gone, calculations like average and max, and the ability to check my GPS in all weather and not worry about whether it'll get dropped/wet/broken, amongst other things, has been a lifesaver. I use a Garmin HC Venture