At eight bucks, Zombies, Run! is one of the most expensive apps on the market, but its success proves that people will pay a bit extra for innovative experiences. Zombies, Run! adds zombified audio to the average workout routine app. In other words, think RunKeeper with the sound of moaning zombies hot on your heels. The app has well over 100,000 downloads since its February launch on iPhone and iPod Touch, and recently expanded onto Android and, this week, Windows.

“People are receptive to new experiences and powerful storytelling,” says Adrian Hon, co-founder and CEO of London-based game developer Six to Start. “One of the reasons Zombies, Run! has been so successful is that everyone wants to get fit and most of us need motivation.”

Behind the app’s complex storyline, which includes 30 missions each lasting 20-30 minutes, is co-creator and novelist Naomi Alderman. Alderman brought the idea to Hon, a friend and longtime runner, in the Spring of 2011. The two moved fast, starting the largest Kickstarter project for a video game at that time and raising $73,000 for its launch in early 2012.

As Hon developed the code, Alderman wrote the scripts, 40,000 words in all, which motivate runners to save a town from a zombie invasion. Runners pick a mission and hear a series of audio prompts that guide them through life in a post-apocalyptic zombie world where they must gather supplies such as water, help others to safety, and run (or walk) from nearby zombies. The app uses scary sounds of encroaching zombies and music to keep things moving along, while maps of the base and graphics bring clarity to the action.

Zombies, Run! clearly derives its storylines from the horror genre, but Hon says it was also inspired by a social theater experiment taking over the streets of Britain. Subtlemob provides an MP3 and secret location where a crowd gathers at a specified time to listen to a composed score along with narration and instructions. From there, a spontaneous performance erupts. Zombies, Run! operates on the same idea of initiating action through sound and story. While the app currently only allows for a solo-running mission, perhaps future versions will include multi-player participation and interaction — imagine a mob of zombie marathon runners.

Hon says the creators of Zombies, Run! will continue to devise new experiences for users, most recently ZombieLink, which offers a run history and playbacks of the best zombie chases. Six to Start is also developing an app that will help first-timers train for a 5k. Not sure if it’ll be a 3.1 mile zombie chase, but it’ll likely be clever and captivating.