Cardiovascular apps
A lot of cardiovascular analysis apps share the same naive mistake. For the most part they display a daily HR average across different periods. They then compare a previous period with the current one. If I have an average of 65bpm in June and now I have 70bpm in July, they tend to mark it as bad. But what if I was more active in July compared to June? Generally speaking, doing more sports, and being active, is a good thing. On one hand I have an indication that my average daily HR is getting worse, and on the other my active minutes are improving.
Perhaps one might be inclined to discount HR data points that happened during workouts. But this is also a naive approach to the problem. If I go for a run for 40 minutes, say from 12:20 to 13:00, my HR is affected for the remainder of the afternoon - stabilizing a few hours before bed.
This is one of many challenges of providing insights into health and fitness data.