Provided herein are systems, devices and methods for the rapid and accurate measurement of analytes by assay of binding events, by direct, digital measurement of individually resolved analyte/reporter binding events. The digital molecular assay systems, devices and methods disclosed herein are capable of particle-by-particle readout using optical reporter molecules that detect and report the binding of a single analyte molecule, and report each such binding in binary format. Such digital molecular assay systems, devices and methods are useful in a variety of applications, such as on mobile electronic devices for use in the field.