When the battery of a connected device is running low there is a notification about that. However that notification disappears after a while. The notification should be persistent/critical just like the notification for the builtin battery
Not sure. But I can see that the mouse randomly stopping to work during a presentation would be bad. Hello Nicolas, patches welcome :p
As a data point, I have a battery powered mouse, the warning comes about a week before I need to charge it. If we were to make it persistent, it might be good to have a much lower threshold as to when it applies. These devices aren't in the region of hours like laptops are.
As another data point, I have a bluetooth speaker that at 10 percent (that's when I get the warning) will last a couple of minutes. It also seems to only report in 10% steps, so any lower threshold wouldn't work for that device
I would lean on the side of making it critical if only because unexpectedly losing power to a connected device is much more annoying (and potentially consequential) then the annoyance of dismissing a notification.