Mass production of consumer electronics devices and market competition have provided users with cost-effective, compact, and high-performance products with high-end components including digital cameras, graphics processing units, and various sensors. This opened up the opportunity for researchers, and even citizen scientists, to develop novel imaging, sensing, and diagnostics platforms using mobile phones as an underlying platform. Mobile phones' hardware and software technical capabilities, wireless connectivity, and wide-spread use, in billions, have made them ideal, especially to address the global demand for accurate, sensitive, cost-effective, and field-portable measurement devices that can be used in remote and resource-limited settings around the world. This Review focuses on these recent advances in the use of mobile phone-based imaging and sensing techniques for point of care applications, including microscopy and diagnostic testing. The achievements demonstrated so far illustrate the potential to globally transform and democratize measurement science in general, with a significant impact for scientists, engineers, and educators.