Zombies! Run! Seriously!  
I found this app Zombies, Run!, “an ultra-immersive running game and audio adventure for the iPhone, iPod Touch, and Android” created by London-based company Six to Start and writer Naomi Alderman. Like other running apps, Zombies Run! will provide you with your distance, time, pace, and calories burned for each of your runs, as well as allow you to play your own music.  
But here is the hook: Zombies, Run! actually gives you a reason to run in the form of a zombie apocalypse story. 

You become a character called Runner 5 and you given a mission. During these missions, you will have to avoid the zombie hordes, as well as collect important items for base camp, like medicine, batteries, and ammunition. These items will be added to your inventory automatically as you run, and it is up to you to decide what to do with them upon returning home. By building up your base camp, you will unlock new missions and new parts of the story. The more you run, the more you will learn about the zombie apocalypse, who is behind it and what the plans are for re-colonization!  
One of the best features is that it is designed to work anywhere and is not dependent on your speed or ability. You can run outside, jog on the treadmill, or take a walk and still participate in the story. The creators achieved this versatility by allowing the app to use both the GPS and accelerometer features of your iPhone, iPod Touch, or Android device. The app will be available in February for iOS. It is currently available for preorder at a 40% reduced price of $12 (or 2 for $20) on their website. Also promising is the planned RunKeeper integration! Yes!