It looks like this is allowed since 2017, with short transmissions less than 1 sec.   Are there any common practices in place for this, like ARPS, etc for sending short digital messages over bubble wrap FRS radios ?

Money talks!...... Unfortunately this was written to focus technically to only apply to the Garmin Rhino GPS/radio. Not many other applications for that precise of a description.

If you dig into the rules, external devices aren't permitted to be attached to FRS. As noted in the prior post,
the change was pretty much made to allow a very short burst for position sharing radios.

The FCC position on FRS is essentially the device has to be used as it was certified. Very few FRS radios
ship with any kind of open port (e.g. speaker/mic jack) and technically if they did the only thing that could
be plugged into them would have to ship with it.

MURS allows data, not explicitly doesn't permit store-and-forward data. So you could do APRS over MURS
but not digipeat.

There doesn't appear to be any significant rules on the 900MHz band spread spectrum radios, so that would
be the best bet if you really wanted to do data. The Gotenna stuff moved to that for this very reason, as they couldn't
legally do repeating on their original MURS product.

Want APRS?  Get ham stuff that does that all day long, parts readily available.
Ham exam too tough for you?  Get a rino or motorola talkabout that pairs to your phone and does messaging and location sharing.

Don't waste your time doing some mickey-mouse hackjob.

Yes, ham I am.  I think 900MHz looks like an interesting angle.  Will have to remember how to do the Esp/Arduino tricks.  
Mickey-mousers run into a lot of cool technology doin their hack job stuff.
Attached File

Every single one of my very cheap FRS radios has a Kenwood style speaker/mic jack.

Technically speaking, with a cable and APRSDroid you can send data simplex.