Try Runtastic Heart Rate
. Its works really good!!! I been using it for along time. You dont need any extra accessories. Just put your finger on the flash light; it will do the rest.
* Measure your pulse with the camera on your smartphone
* See your HRM results in a graph
* Variety of different, instant measurement types: resting HR, maximum HR, and HR before/after cardio
* Upload, store, and analyze your exercise results on the runtastic fitness site, www.runtastic.com
* Share your HRM results via your social networks: Facebook, Twitter, Google+ and E-mail