Index Sleep Monitor

Garmin Index Sleep Monitor is an armband from 2025, sitting in the mid-range band at an indicative $169.

It reads 11 of the 33 signals this comparison tracks. Nothing at all from body composition. Rarer readings it does take: Body Battery.

By sensor class: 10 at high accuracy and 1 at consumer grade. That grade is my classification of the hardware, not a lab test. Those readings come from an optical heart rate sensor, an optical blood oxygen sensor, a skin temperature sensor and an accelerometer. Blood oxygen is measured through the night, not continuously through the day.

Its 7 days per charge are the 8th longest of the 11 devices of its kind here that publish a figure. Rated 5ATM / 50m. It weighs 30 g. No subscription is required.

Upper-arm band for nights only, June 2025. Works without a Garmin watch, but records no steps, workouts, distance or training load, and does not broadcast heart rate.