NOTE: This is only for people running Android Wear 2 Preview build on their LG Urbane 2 and Huawei watches.
Since currently there is no Theater (Cinema) Mode in the Wear 2 Preview (at least on Huawei Watch AFAIK) this app will simulate Theater Mode by simply showing a black background once you start it. To exit the app click on the watch button.
Tested on Huawei watch.
I also recommend turning off ambient mode on your Android Wear watch, so that the power to the display is turned off after some time. I recommend this because even though Huwaei watch has AMOLED screen, it seems to have a pinkish hue when it should be completely black. Turning off ambient mode helps resolve that problem.