I'm working on a project that requires multiple ESP32s to be able to receive a signal from a smartphone in order to close/open a set of doors. The catch is that this will be happening in a remote area with no internet whatsoever, and on a wide scale (hundreds of ESP devices). The setup also needs to be portable, as it will be moving around a lot. What is the best way of going about this sort of local network? So far I have considered:
LoRa (just not sure in general how this would work with a phone + esps locally. And phones can't send LoRa signals, can they?). Another problem with LoRa is that the antennae that need to be hooked up to my ESP32's for LoRa to work are too bulky for my situation.
MQTT (relatively low range, requires routers peppered throughout. Small number of devices/clients that could be connected if the broker is a device like an ESP or a raspberry pi)
Mesh network (devices can be connected with painlessMesh; seemingly ideal solution. Just having difficulties figuring out how to connect this to a smartphone (both to receive and send messages))
Does anyone have any suggestions?