I've had a few over the years. Lots of promises and gimmicks. Like the newer ones that don't need a chest strap. Well, IMO most of those aren't very accurate or timely.
The lower priced Garmin with the chest strap seemed to be the one I could count on to actually monitor my heart rate and recognize when it was elevated due to a set at the gym or running or what ever. I won't buy another fancy one.