You're jogging at a steady pace, enjoying your favorite music through your headphones. Your breath is short and your heart is pumping. Your legs feel like they couldn't carry you any faster.
And then you hear the groan of a zombie over your right shoulder. It's sprint or be eaten.
The zombie apocalypse isn't upon you. You're just taking part in the latest fitness craze -- smartphone apps that make a fun and interactive game out of your daily workout.
Software developers are taking advantage of smartphones' advanced technology -- GPS, accelerometers, MP3 players -- to create "immersive" fitness games that appeal to both avid and reluctant exercisers.