These are the current best selling sleep trackers at Amazon.

SaleBestseller No. 4
Fitbit Flex 2, Black (US Version)
4166 Reviews
SaleBestseller No. 7
Fitbit Alta HR, Black, Small (US Version)
4193 Reviews

Details and pricing last updated at 2018-12-15 at 12:54 . Links and images via Amazon Product Advertising API