...there are some show stoppers, at least when using LEO birds. It takes a fair amount of theoretical understanding to get to the point where operating practice can yield functional capability.
Agree completely.
That is why I think a very thin slice of this puzzle is the LEO APRS channel where the sender needs zero knowledge about satellites. He just sets his emergency outgoing message into his APRS radio or TNC, and leaves it running for a few hours, and he can be assured that his email is delivered.
If ISS is working, then return messages to the mobile are possible.
Again, not at all suggesting that this detract even the slightest from the great initiaves that are now underway for real-time EmComm. But because it is there now (sorta) and is so easy to add to, and can be used by anyone with even the basic understanding of a TNC or packet (though that knowledge has really deminished by an order of magnitude since the 80's and 90's), I think it is worth practicing.
Also, this EmComm low-rate outbound Email concept has spawned a new look at 6 meter Meteor Scatter comunications using the cheap 100W 6m radios that are so easy to find these days. If we just add 6m receivers to many of our existing APRS Igates, then an emergecy email can be transmittied out of an area for an hour or so and have very good probbility that it was deliverd.
See the web page: http://www.ew.usna.edu/~bruninga/meteors.html
With the global APRS network listening 24/7 everywhere for messages (on VHF, HF, Satellites and now Meteor Scatter, only the sender has to SEND his EmComm Email report, the rest is already done.
Bob, WB4APR