When trying to identify a mystery device, it would be helpful if the Sense app could show me a simple log of when the device turned on and off. There isn’t an easy way to get this right now. You can get on/off times from the timeline but that shows everything not just the device that I’m interested in. Would be great if I could filter the timeline to show only one device. The closest thing today is the device power meter but that can be difficult to use since on/off events can be spread out quite a bit requiring a lot of zooming out and that point it’s hard to pinpoint exact on/off times.
It’s not exactly what you’re seeking, but tapping on a Device in the Devices screen can give you some of that info, though more so in aggregate. The Usage card can tell you how many times the device has been on for Day/Week/Month/Year/Billing Cycle as well as the duration it was on and the usage. You can kinda extrapolate from there (again, not perfect for what you want).
I have to disagree about difficulty determining when a device has turned on or off. Instead of going to the timeline, visit the device page. Select the device your wanting to view and use the power meter there. You will be seeing use for only this device instead of everything on the timeline