Grey: Hourly would be great. I like your bar graphs and think they are really easy to read at a glance. So, a 24 hour bar graph? If you can drill down to the hour... cool! I am sure someone at some point will want to see what every hour of the day would look like. But for myself, just 24 straight up lines is perfect especially for strain & possibly stress.

Andrew Sardone: Got it. Stress chart is coming soon for Apple Watch.

To summarize, for Strain day view, you basically want to see a chart to see how your Strain increases throughout the day right? Like by minute/hour

Grey: Dude, that would be spot on perfect!!!

Yeah it would be cool if where you have the option of W,M,Y on graphs.

It would become D,W,M,Y. This way you could standardise adding a day view to certain graphs that require it letting the user see exact figures during the day for certain graphs.

A second example this could be done is on the daytime HR graph, an option to select D instead of W would allow the user to see his heart rate during the day. Thus he could see when he was working out or sitting at a desk.