If you have a smartphone, then you can use the customizable capture templates[1] (similar to Emacs) from organice. You can even use bookmarklets to capture web content, and have Siri integration.

Limited networking is not a big issue, because organice can cache your Org file locally until you can sync later.

If you do get around to building an SMS to Org mode gateway, I'd be interested to see a post about it, though. Good luck with it!

1. https://organice.200ok.ch/documentation.html#capture_templat... 2. https://organice.200ok.ch/documentation.html#bookmarklets 3. https://organice.200ok.ch/documentation.html#siri_integratio...