Idea: Open Wifi server for showing outdoor temperature

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?

No internet connection is needed so I think this could be safe.

Do you mean shown only on phones connected to your WiFi or do you mean shown on phones anywhere?

10.255.255.123

Don't allocate static IP addresses in the middle of the DHCP range, use ones at the start or end of the range. Best to leave the device getting the IP address by DHCP and locking the IP address in the router to the MAC address of the device

I have something similar on my network passing outside temperature and other weather data between ESP8266 boards. No phone access though.

"Do you mean shown only on phones connected to your WiFi" Yes, that is what I mean. I hope that whenI use a fixed address I don't need a connection to a DHCP server or a router.

If you mean the phones will connect to the wifi on whatever device you use then that device will at least have to provide DHCP for the phones to get an IP address themselves. Make the wifi device IP address static at the beginning of the range, ie .1