vivosmart 4 and chest strap

I'm considering a vivosmart 4 coming from fitbit charge 3.  I'm looking for a decent activity tracker mostly interested in 24 heart rate and sleep tracking, no real interest in smart watch features.  I like the battery life and form factor of both vivosmart and charge 3.  I understand fitbit maybe ahead in the sleep area.  I like what i've seen of the garmin app and data.  I also have come to understand optical heart rate monitors just don't seem to cut it for intense or near intense exercise. 

I mostly do elliptical and indoor rowing.  I've found the heart rate data during those exercises to be pretty much useless, and don't expect the vivosmart 4 to radically improve over the charge 3.  I'd like to be able to use something like the vivosmart all day, but substitute the Heart rate data only during exercises with a chest strap monitor.  

Are there any use-cases where something like this can be achieved?