Setup for the later version, Shelly Plus 1, is found here !!
S1 is a WiFi switch, 16 Amps, with dry contacts and the function "without Internet" + that the S1 can use a 12V DC source makes it perfect for an "use case" in a boat/mobile home.
It's compatible with Alexa, Google or HomeKit using HomeBridge or as a "native" HomeKit device using Mongoose firmware(Flashed via a standard WEB browser !)