If Vic cannot minimise Covid with their lockdowns, to me neither could SA, even with our mask wearing and QR check ins etc. So returning SA residents (with potential Covid) can either stay in NSW or Vic, stay in a special Adelaide medi-hotel room for 14 days at $ cost ( if there are vacancies), or opt in for the App with relevant Tracking/police checks etc and self isolate at home..

I know what alternative I would chose if coming from interstate or OS.

At the moment it appears to be a voluntary trial only and could be a useful tool to keep track of people in self quarantine, but could have serious consequences if misused or extended for other purposes, ie travel between states, tracking of citizens etc. But our leaders wouldn't do that would they. On another note it will be interesting to see how our premiers use vaccination records to enable travel between states. I fear that a vaccination visa/passport would be the end of free unimpeded travel throughout Australia.