In all honesty, you have a ready and tested solution for minimal data in a very low bandwidth and low latency situation such as satellite communication on the open sea (Iridium etc.).
This is in the form of saildocs.com as the GFS data content provider (free) using a satellite optimized mail service such as mailsail.com or xgate (not free). All you need to do is set background processes to disabled and/or set your firewall to pass only emails (pop and smtp). Sending the requests and pulling the responses can be scripted if desired.
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