The dim light melatonin onset (DLMO) is the gold standard circadian phase marker in humans. We previously developed a proof-of-concept home DLMO kit and demonstrated that valid DLMOs could be collected at home, with objective markers of light exposure and sample timing. Nonetheless, the proof-of-concept kit uses costly external technologies such as photosensors (to monitor light exposure) and MEMS TrackCaps (to monitor sample timing). We have designed an iPhone app that: (1) streamlines the home DLMO collection procedure, (2) maintains the objective assessment of light exposure and sample timing with internal app features, (3) provides real-time feedback on errors in light exposure and sample timing to both participants and externally located researchers, and (4) provides some cost savings over the original proof-of-concept kit. Programming capability includes options to (1) sample saliva at half-hourly or hourly intervals, (2) end sampling at participants’ habitual bedtime or up to 3 hours past habitual bedtime, and (3) set a light intensity threshold of choice to alert the research participant and externally located researcher in real-time that melatonin levels may be suppressed. At the conclusion of the home DLMO collection, the app generates a report of light levels and sample timing for the researcher. Saliva samples can then be sent to a qualified laboratory for assay processing.