Chris Green wrote:

> Are there any simple 3G/4G add-ons for a Pi that will allow it to
> power up into a mode where it has the ability to be connected to via
> the mobile data connection?

Not really, if the 4G connection is down, there's no remote way you can
ask it to come up, you could do something custom like sending an SMS to
the dongle (if the SIM supports SMS in addition to data) and have
something running on the Pi to bring up the 4G connection in response
(and maybe text you back the IP address it has)

The other possible wrinkle is that even with the 4G connection up, it
may be using CGNAT which doesn't allow inbound TCP connections, just
outbound, so again you might homebrew something that brings up a VPN
tunnel from the Pi end over the 4G, then you can connect though the
tunnel ...

--- SoupGate-Win32 v1.05