So I now have wired a Raspberry Pi to a garage door remote, created a primitive web interface for it, and attempted some security and stabilization for the supporting applications. Now I am moving on to sending an e-mail with photo attachments of security events that have occurred.
Setting up the mail server within the Ubuntu distribution was a bit of a pain. The Pi can't act as an MTA all on its own thanks to all the relay rules in place across the Interwebs, so instead I had the default exim4 installation route through GMail. I wasn't interested in installing yet another outbound mail system; I would rather leverage what comes packaged by default. I ensured I deployed an application-specific password for exim4, then followed the very helpful instructions from Debian on how to hook it all up with GMail as the outbound SMTP relay.
The default mailutils will not send attachments over e-mail, so instead I installed mutt for a command-line mail client. I can issue e-mails via:
echo "Motion was detected" | mutt -s "Garage Security System" -a /srv/motion/23-20131030184606-00.avi -- email@example.com
Once combined with Motion's External Commands, I can build scripts that e-mail off movie files as soon as they end. The mpeg4 format appears to work natively within Android, so video snippets are easy to view once they are e-mailed out.
Now for some polish; I need to construct/find an enclosure and finish the front-end user interface.