The LG G Watch and Samsung Gear Live both lack a light sensor to adjust screen brightness, which is kind of a pain. The Moto 360 is supposed to have have an ambient light sensor, but Display Brightness for Wear lets you fake the same functionality on the G Watch and Gear Live. It uses the time and your phone's location to determine how bright the watch should be, which is pretty clever.
The app uses coarse (network) location on your phone to figure out about where you are and uses that to calculate sunrise and sunset times. If it's night, the watch brightness is always set to the lowest level. During the day, brightness will be set to either medium or high depending on what you're doing. If you're driving, for example, the brightness will be set to high. If you're standing still, it goes to medium.
It's not clear if there are more types of activity detected, but it's possible more could be added even if driving is all it has right now. It's still a nifty way to get around a design shortfall.