There are a few devices that can be controlled via RF4CE (Zigbee protocol).
I expect that most of them can also be controlled over IP so there might not be much need for such a thing … but I was wondering if a Zigbee source (like Conbee) could be used to control a set-top box.
https://zigbee.org/zigbee-for-developers/network-specifications/zigbeerf4ce/