The Harmony Hub can do a lot of the AppleTV features. I'm guessing that the Siri remote behaves somewhat like a track pad. When I say "track pad" I mean it in the laptop pointing device sense as opposed to a "joydisc" that sends compass directions. If it is really more an matter of sensing direction, the joydisc on a Harmony remote may well work.
The K600 appears to be uniquely designed for name brand televisions.
It supports Windows, Android, and iOS not just TV's. I assume AppleTV is iOS but I don't do fruit. Worked with my FireTV sticks/boxes too. Controls a laptop I have stuck in a cabinet HDMI'ed to AVR and OLED. Supports Shield. Probably even my phone. best thing is it uses dedicated receivers so you don't have to fool with pairing.
Link to K600
System Requirements
Bluetooth®
Windows® 8, 10 and above
macOS® 10.12 and above
WebOS (LG) v3.5 or later
Tizen (Samsung) v2.4 or later
Android TV v6 or later
Android 5.0 or later
iOS 5 and later
Unifying
Windows 7, 8, 10 or later
macOS 10.11 and above
Android TV v6 or later
WebOS (LG) v3.0 or later
Tizen (Samsung) v2.4 or later
Chrome OS™
USB port or Bluetooth low energy technology enabled device with keyboard support
Internet connection (only for optional software download)