more fantastic insights, thanks mate!
particularly good observation on "the extra alerts or warnings and the like you have to acknowledge?"
my ambition is to find a use for very old / broken cell phones. phones which already have "broken" buttons, or battery issues, or a broken screen for example. these phones tend to have keypads which are two copper circles (one inside another), easy to solder to and then to wire up to a relay or switch... or microcontroller?
with older phones (I'm thinking of simple nokia in particular), the nagivation is really simple and I think the surprise alerts and surprise warnings could be navigated around by simply starting each command routine with two presses of the "hang up" button.
this is sort of similar to the "turn screen off then back on" thing that you were talking about, which is pretty standard on modern phones and smart phones.
I reckon this project is quite doable...
check out this for example, http://www.anthony-dacko.net/Cell-phone ... phone..htm
but this guy uses DTMF (dual tone multi-frequency) sounds (standard telephone tones) as the means of communication.
this means his projects are reliant on using old cell phones with an "auto-answer" feature.
for his alarm dialer projects he relies on old cell phones which have "fast dial" or "one touch dial" features... where you press one button to dial a pre-chosen number.
but the punchline is that such old phones, particularly nokias, are actually in some abundance. and they're cheap of course!
there are loads on ebay going cheap, so it's quite feasible to include one cell phone for each microcontroller in a given project or projects. both parts are cheap and low power lol.