You get the app "Runtastic Pro" for free.
By clicking on the link, you are redirected to a promo site from Duracell. Insert some fake information and use a temporary email like http://www.10minutemail.com.
For the required "battery number" use 8 numbers and 2 letters (no matter what, e.g. 12345678eg). Upload a picture - no matter what.
You get a code which must be used in the "normal" app. So either you already have it or download it from the app store.
Where to enter the code?
Runtastic Lite > Settings > Runtastic > Enter Promo Code