I've been using this nifty little app on my iphone for a while now and it's great for getting me out of the door when I really can't be bothered to go for a run. Maybe it's the geek in me but there's nothing like the sound of a zombie horde bearing down on you- intent on munching you down like a meaty tube of pringles- to force that extra little burst of effort from your tired legs.
It's a bit pricey but it's kept me entertained when I'm out running and more importantly, when I'm contemplating suicide at the prospect of another treadmill run. The in game commentary interspersed with your music adds a little spice to a run and breaks the monotony of song after song. The prospect of going on another mission has dragged me out of the door more than a few times when otherwise I might have stayed in and endured Corrie, Eastenders etc