I have multiple android devices that need to operate in areas with limited network connectivity. At the same there, I need the data capture on one of them to be immediately available on another device in the vicinity. The different devices can connect to one host device which can host the wi-fi and hence be in the same LAN. Then, what are some good ways to use the host device as a server that can persist and expose data?
This is fairly simple actually. With "ssh server" (ice cold apps is a good one), you can install it on each android device, and then connect from one device to another across your Lan. Of course if you have no network connectivity you won't be able access the Web, but it should be possible to push pull data using rsync (you will need busy box and root to gain full functionality), but it is certainly very possible.
Although, depending on what you actually want to achieve, some easier options are available - eg for simple file sync, you can use bittorrent sync, even without an Internet connection