The "Iphone sensor" community program does work, and works rather well.
It relies on a fixed static ip being assigned to each user whenever they sign into wifi.
When that happens, they are marked as "present". Although it says "iphone", that's not really the case.
In addition, many users have combined that "presence sensing" with other types of presence sensing - from the Hubitat app, or from other means (such as a smartthings sensor). There is a "combined presence" community app that also works well.
Finally, using that in order to do a notification, is not that difficult, in rule machine, or in the notifier.
Setting up your Alexa devices as TTS notification devices requires some skill, and the Echo Speaks community app.
