A free app for Android, by Appestry.

Remote Gear for Roku is a smartwatch app that makes it easy to control your Roku device from your wrist. It’s compatible with both the Samsung Gear and the Google Watch. You can choose which Roku you want to control using the phone app. You can do things like play or pause a stream, go back to the main menu, change the volume, and switch channels. You can also control the playback of media on your device.

The best part of this app is that you don’t need to download anything. You just need to make sure that the smartwatch and phone are connected to the same Wi-Fi network.