I have an idea of showing local temperature on my phone. And everybody elses phone too. No internet connection is needed so I think this could be safe. In this case I think there is no need for passwords and user ids. Wifi IP could be a fixed local IP, like for example 10.255.255.123
I know about Lan shield and ESP32. And I hope that code cannot be changed via wifi, I have code and HW for PT100 temperature sensor, and there are examples of Wifi servers.
What do you think? Safety, what HW, what SW. Does this idea work?