Automount USB drive when connected

[Cerebus]

I have a USB enclosure that I'd like to  be able to walk up to the machine and plug in  and have a series of things happen:

1) Disk mounts in /mnt/backup (or wherever, the key is it mounts without intervention)
2) a backup script I specify runs when the disk successfully mounts
3) when complete /mnt/backup unmounts 

I've got step 2 (mostly), and step 3 is trivial, but I can't get step 1 working

(To be clear, this disk would never be present at startup. Basically, walk in, plug in drive, let the backup run, unplug the drive, and leave. I want this to work without requiring anyone to login)

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ADVANCE TO THE REAR!