Barriers to effective screening and management of NCDs in resource-constrained regions include limited availability of trained personnel, access to affordable automatic medical devices, and longitudinal clinical data. We present an end-to-end mHealth system which takes advantage of the almost universal availability of smartphones in order to address these barriers in a scalable and affordable manner. Our system includes simple, low-cost ($5–$20) and open-source peripherals that allow a minimally trained person to collect high-quality medical data at the point-of-care through a standard smartphone; allows the reliable transmission of clinical data even in the case of high-latency network connections; stores data in a cloud-based system, making patient records accessible anywhere; and enables both crowdsourced diagnostics and generation of annotated data for the research and development of automatic decision support and risk assessment systems. We show examples of the different elements of the system tailored for the management of cardiovascular disease and chronic obstructive pulmonary disease, which includes prototypes of the low-cost peripherals. In a validation study (of 40 volunteers), our smartphone-based blood pressure (BP) monitor was shown to measure BP, heart rate and respiration rate with a mean-absolute-error of less than 5 units from the reference values for 80% of the measurements.