Pulmonary rehabilitation is a behavioral intervention that can improve symptom control and quality of life for patients with chronic obstructive pulmonary disease (COPD), but access, uptake and adherence are problematic. Our team has pursued the development of a mobile phone-based intervention (mobile pulmonary rehabilitation, mPR) with iterative design and a pilot study. The mPR intervention is delivered through two technologies: text messages (SMS) and a smartphone application. Our user-centered design analysis of pilot study data led to several insights. First, patients’ replies to the SMS suggested that messages were anthropomorphised and provided social support. Second, the smartphone application could help patients by clearly visualizing the exercise program, alternative exercises, and progress to date. We demonstrate the design iterations made to meet these requirements and we present feedback obtained from experts and from four COPD patients. We discuss implications for the design of mobile pulmonary rehabilitation interventions.