On a related "note" -- see what I just did there? ;-)
I've just purchased a reMarkable (TM) tablet. I'm not ready to say it's the greatest thing ever, since I haven't really poked around with it much yet, but I was looking for two separate products:
* a device that's particularly good at reading PDFs (without trying to be good at everything else).
* a device on which I could sketch.
I'd looked at a few devices -- most notably Sony's digital paper product and Wacom tablets -- and the reMarkable seemed to be a reasonable compromise. Also I was impressed when I saw a guy at our local hackerspace using one. (In fact, I was unaware of the product until I saw him using it and said "Cool!")
Here's the tie in -- more of a fantasy at this point: One of the selling points to me was that it's got a modified Linux under the hood and one can SSH into it. The company also offers a cloud-based feature that promises to turn handwriting into text...
That last tidbit looks like the promise of StaffPad. Given the sorta-kinda open sourciness of the reMarkable, I wonder if the company could be nudged into going beyond handwriting translation to notation translation. The reMarkable wouldn't do playback, but if the cloud service is brainy enough to do a decent translation, it might be possible for it to "Save as..." MusicXML or some such, that could then be massaged by Lilypond and / or MuseScore 3 and / or whatever else is out there, and one can SCP files to and from the device...
It may be that a more general purpose device from a more proprietary company, using more closed source software would do a better job, but I'd rather try to stay a bit closer to the open when possible.
Anyway, just a thought...