[16]

I have a second SIM card that T-Mobile gave me for free (no idea why). I have it installed in an Android phone running Tasker with a bunch of jobs I created to do various things. Android phone stays at home while my primary (flip phone) comes with me. I get specific Matrix (https://matrix.org) messages forwarded to my flip phone, I can query the weather, I have a couple RSS feeds forwarding, and I can enable/disable any of these tasker profiles by sending custom commands from the flip phone back to the android. Obviously this requires having a second SIM card, but you could probably find a super cheap talk/text (or text-only?) prepaid plan temporarily and set up something similar. Tasker is extremely powerful and could conceivably do most if not all of what you're asking.

[beaconstudios]

you could also use Twilio to build an SMS inbox API and do it without any hardware.

[notRobot]

That's so cool!

Q: How do you get Tasker to read Matrix messages?