For some reasons I thought that Pebble Smartwatch with Pebble OS 4.x does not
communicate with Ubuntu Touch devices. But I was wrong. It does (the Pebble
Time Steel and the RockWork app on the Ubuntu Touch).
I still think that Pebble 2 does not work with the RockWork. But it's not my
problem as no I have only the older Pebble Time Steel. :-)