This report summarizes the challenges and lessons learned during a pilot study of an mHealth tool that had been carefully crafted using iterative user interface design and human factors principles with much input from both clinical and patient users throughout the design and implementation process. PocketPATH: Personal Assistant for Tracking Health is among the first patient-oriented mobile health applications shown through a randomized controlled trial to benefit patients' self-care behaviors and health out comes compared to usual care. It is also one of the first systems designed with both patient and clinician interfaces (Pocket PATH Link).