I have a security DVR purchased from Astak. It's software is Windows-only, using some proprietary plug-in, and although the DVR can FTP the .AVI files up to a server, they don't display on the Mac.
So, long-story short, this line will convert the format into an Apple-friendly .MP4:
/opt/local/bin/ffmpeg -i "$1" -acodec libfaac -vcodec mpeg4 -flags +aic+mv4 "$1".mp4
I set the DVR to FTP to my always-on Mac server. On that server, I set up Hazel to watch that folder and run the previous conversion shell script on the incoming .AVIs. I toss the .AVIs in the trash and move the .MP4 files into Dropbox, where they will synch up with me wherever I am (and, helpfully, provide me local notifications when the movies are created).