Lock/Sleep on when lowering the hand (opposite to wake up on raise)

[darkdragon-001]

Often, you just want to have a look on the watch. This works well with the raise to wake up option. When you are done, you usually want your watch to sleep again. While double-tap works to wake-up and sleep, there is currently no sleep event triggered by the motion sensor. What are your thoughts on this?

This might be related to #578, #618, #697