As Idolse already mentioned, with a jailbroken iPhone and Netatalk installed ( under Mac OS X ) your iPhone mounts like any another computer ( it IS a computer
) you have in your network. You can use the finder to search for books ( i.e. ext. ".prc" extensions ). You can copy,transfer, move etc.
Regarding device detection - I add my books fromthe iPhone to the Calibre over the wireless network since I installed Calibre.
Idolse, if you want to automate some of the steps using Automator or Applescript is really straight forward.
The only thing left is the missing plug-in to deDRM your books.