>Some of the highest end railroad watches featured what was referred to as an up-down wind indicator. This is called a power reserve indicator on modern watches

>Some of the highest end railroad watches featured what was referred to as an up-down wind indicator. This is called a power reserve indicator on modern watches, and it visually communicates how much wind remains in the watch on a sub-dial at 12 O’clock. I now want this as a battery life indicator on a smart watch.