I’ve been using the Morpheus HRM + app lately. One thing I really like is that it asks a set of questions in the morning and looks at HRV, then makes a very good recommendation on what the HR ranges are for your zones that day. For example one day my peak zone 2 might be 140bpm while another day it might be 136. I find these to be pretty well correlated to my RPE.
Could bevel do something like this?