On an Android phone you can use Tasker (~$3.50 US). To monitor connecting and disconnecting from your wifi as your presence triggers. It is very reliable.
Then you need Tasker to relay the message to ST via SharpTools or Alexa. You need a SharpTools/Tasker plug-in (~$3.50 US) or Alexa Buttons/Tasker plug-in (~$3.50 US) to do that.
I use SharpTools for this. SharpTools is free to use other than the plug-in for basic routines.
So total cost is about $7.00 plus tax in US.