The Fitbit/Pebble team have promised to maintain "most" of the current functionality for the 2017 calendar year. After that it's anybody's guess.
By Nicholas Tsiotinos on January 1, 2017
Very accurate compared to my chest mounted Zephyr HxM BT Wireless Heart Rate Sensor. On my recent HIIT ride, they sync'ed pretty much beat for beat... But, the watch can move around it bit, so it might slip out of "optimal" position on your wrist. But, it is capable of pretty accurate measurement, it would seem.
By Gene Goodell on April 29, 2017