The Index Sleep Monitor tracks sleep stages, heart rate, and even your breathing to create a “comprehensive view of overall fitness and recovery,” with a personalized sleep score delivered every morning so you know how well you slept, according to Garmin. The Index Sleep Monitor is now available through Garmin’s online store in S-M and L-XL sizes for $169.99. The tracking is handled by a small, removable electronic module that features motion sensors and an optical heart rate sensor that Garmin says will run for up to seven days between charges. For those who prefer to charge their watches at night so their battery is full every morning, the Index Sleep Monitor provides an alternative way to track sleep metrics that’s also free of distracting notifications. The Index Sleep Monitor does have vibration capabilities, but they’re instead used as part of a smart alarm feature that only tries to wake you during lighter sleep stages.