Android/iOS: You have a lot of options for apps that will track your run, but few of them help you train and improve your times. My Asics is an app that features an adaptive system that looks at your runs and helps you improve your times.
Where a number of apps out there want to log your runs, My Asics wants to make you better at running. You start by setting a goal and your current times. Then My Asics builds a distance, pace and training plan around that for you. As you log your runs, My Asics changes your plan to push you harder. During runs it sets the pace for you and will have you run harder when it tracks your improvements.
The end goal is to shave a few minutes off your overall times, and My Asics seems to do that pretty well. It's lacking some features of other running apps, like a full on map, elevation and (weirdly) kilometres, but it does a great job of training you to improve your times nonetheless.