I play a lot of video games. But I don't play a lot of video games that force me to go outside and run around my neighborhood.
That's the appeal of Zombies, Run! a game for iPhone, iPod Touch, and Android that's more of a podcast than any sort of interactive entertainment. It's a game you actually have to go outside to play. (Sure, you could use a treadmill, but come on.)
The way it works is simple: You load up the game, plug in your headphones, and go for a run (or jog, or walk). As you move, your ears will be pumped with pleasant British voices that tell you all about the trials and tribulations that face the residents and runners of post-apocalyptic civilization.
While running, you'll pick up random supplies like batteries, medkits, and ammo. You'll also meet zombies, some of whom are connected to those disembodied British voices (whom you'll grow quite fond of as you travel).
In between each mission, you get to listen to your phone's playlist, which is great as it allows you to rock out to "Call Me Maybe" marathons before each zombie attack.