have you implemented any way to communicate the IP address of the ESP after the user the user configures the device to connect to the network ? or is the user suppose to find the IP address for the module by other mean eg. connecting to its wireless router interface ?
I'm using SSDP for windows discovery (network neighbourhood) and mDNS for Apple (Bonjour on Windows also works), so you don't have to enter the IP address (you can still check in your router's DHCP table for the device's IP address though).
i haven't looked into SSDP yet but i looked at mDNS and it works but as you mentioned you need to have bonjour on windows and avahi on linux - but i doesn't work on Android devices, no support also i didn't find a workaround as bonjour provides for windows