Got this touch screen switch for testing from one of the z-wave manufacturer, tested with my UK hub, ST able add it easily and identify it as Z-Wave Switch. Turning on / off the switch will trigger the status update in the ST app almost immediately.
The switch do not need neutral wire to work (the 3 wire) but come with a relay box.
Quite easy to install & a good deal consider it’s cost (+relay)
This is the prototype before replacing my wall switch 
