The major motor symptoms of Parkinson’s disease (PD) are bradykinesia (slowness of movement), rigidity (stiffness of limbs), and tremor (rhythmic shaking of extremities). Measuring the presence and degree of these symptoms in each patient requires an in-person clinical assessment by a trained neurologist. The increased burden of an in-person assessment has led to a growing interest in the capabilities of wearables, such as a smart watch, or other devices or apps that could track symptom severity outside of the clinic. We tested whether a simple 30-second repetitive alternating finger tapping task on an engineered keyboard could provide validated metrics of each of the major motor symptoms of Parkinson’s disease in a large cohort of PD patients and healthy control participants. We found that this simple task could provide quantitative metrics for all three of the major motor symptoms of Parkinson’s disease. This allowed the ability to distinguish patients with Parkinson’s disease from healthy controls, different subtypes within Parkinson’s disease, and to track symptoms over time as the disease progressed.