Current surveillance protocols after peripheral interventions still use a "one-size-fits-all" model. Unfortunately treatment failures don't follow a predictable pattern and are far too frequent. Since peripheral artery disease (PAD) directly affects a person's ability to walk, finding concordance between activity and burden of disease becomes really interesting. We have developed a mobile research app to study and clinically validate activity tracking using a patient's personal mobile device. These devices were not calibrated and designed for our patient population with cardiovascular disease. We discuss our approach and experience testing the iPhone's performance in a supervised setting to lay the foundation for a personalized surveillance program.