That's an incredibly good question. (Which, roughly translated, means I don't have a clue )
I copied this from a template and learned everything from just playing with it (Sling will never give you any information on things like that). Unfortunately the Channel Number display always worked so I never looked into it.
Guess I better try and figure out how it works. I'll get back to you.
In the simplistic implementation, the soft remote would only know the channel number after the user did a direct entry of a channel number. However, accurate channel number identification would be lost when favourite keys were used or a local user utilized the real remote. Then the soft remote would be out of sync again.
Thinking about this issue for a few moments leads one to the conclusion that the Slingbox must be told by the stb what the channel number is after every channel change to maintain synchronization. The only way this could happen is if the stb had an IR transmitter and was sending messages to the Slingbox IR receiver which we know they have ... else the new learning setup of the web based install would not work. Hmm. what stb's have IR transmitters to give feedback to the IR remotes?
Hmm ... the original Remote.xml must have been written for a high end stb with a 2-way IR system. Am I overthinking this? What was the basis of the original template?
I checked out CustomTuner and all I saw was Channel 000. I added the channel number to the CustomDevice and got the same Channel 000
I've been trying to figure this out for hours and the answer came to me at 03:00 this morning
The Channel Display is designed for use ONLY with the built-in tuner of the Slingbox not with any external device. Obviously the Slingbox knows which channel it's tuner is on so can drive the display. As you said, it cannot know what channel an STB is on so it just displays zero.
So I'm afradi you cannot add it to any remote designed for use with an external box.
Now that makes sense and of course I would not recognize this because I didn't realize there was a tuner in the HD until you pointed it out.... because I only have SOLOs here. All my effort is with satellite stb's ... no QAM tuner required.
Hmm, now what we need is a satellite receiver with an internal Slingbox. Ah ... Dish has those!
Thanks a lot for working this through with me.