To get back to the OP's question:
We simply run our stuff locally, hosted on a laptop (WAMP, Node.js, etc.). We have old D-Link bridges (pre-2012) that are no longer legal/in use, so we use them in
bridge mode (the same as if you were using a tethered robot) with
wired ethernet connections with static IP addresses. We can link up to 4 scouting laptops in this fashion (four clients if you're not using a dedicated machine to host).
If you're using data in your app from the Internet, see if there is a way to cache it in your application. If you're using PHP/Node.js, there are easy ways to serialize objects--PHP has built-in serialization and supports JSON, Node.js has JSON, etc. I'm not familiar in any way with Ruby, but
it doesn't seem too hard to serialize there either.