Garmin HRM-Fit
It runs up to 12 months on a CR2032 at 1 h a day and clips to a sports bra. It suits medium- and high-support bras only, and it is rated 3 ATM against 5 ATM on the HRM 600.
What the maker states
| Battery | 12 months, CR2032, using 1 hour per day |
|---|---|
| Weight | 53 g |
| Water rating | 3 ATM |
| Heart rate sensor | Sports bra clip-on, heart rate and HRV |
| External sensors | ANT+, Bluetooth (3 connections) |
| App | Garmin Connect |
| Stored sessions | Stores heart rate for stand-alone use |