COLMI is a Chinese consumer electronics brand that sells low cost smartwatches and smart rings. Its wearables are worn on the wrist or finger and cover activity, sleep and heart related tracking. Different models connect to COLMI Fit or another supported phone app.

How it works
Optical sensors shine light into the skin and measure changes in reflected light as blood moves with each heartbeat. Motion sensors record steps, exercise and periods of rest. The app converts these signals into heart rate, blood oxygen estimates, sleep duration, activity records and other wellness summaries, depending on the model.

Key considerations
COLMI sells many devices through different retailers, and their sensors, apps and advertised features are not consistent across the range. Low price also comes with limited independent validation. Blood pressure, blood oxygen and sleep outputs are wellness estimates and should not be treated as clinical measurements.