A system, methods, and apparatus for biomolecular measurements, monitoring, and tracking uses a smartphone-based system. A biological sample, including, but not limited to blood, saliva, biopsy, or sweat, is collected on a modular diagnostic test platform, which is then inserted into a smartphone accessory. Optical, electrical, mechanical, or other means are used to transduce a biomolecular binding event, including antibody, aptamer, enzymatic, base-pair matching, or other biological recognition reaction and communicate the results with the smartphone. Some specific examples of targets include 25-hydroxyvitamin D, folic acid, DNA, or proteins from infectious agents, and zinc. The result can then be presented quantitatively or turned into a more consumer-friendly measurement (positive, negative, above average, etc.), displayed to the user, stored for later comparison, and communicated to a central hub location where medical professionals can provide additional review. Additionally, social media integration can allow for device results to be broadcast to specific audiences, to compare healthy living with friends, to compete in health based games, create mappings, and other applications.