I need this just to be able to test how the machine responds to the first time a device is plugged in - without needing an unlimited supply of 'new' devices.
I connected a 'foreign' iPad [my partner's, not synced to this machine but to her own] to test Photos app's response. It auto-launched.
Now I want to try again, let it 'see' the device for the first time - so I'm trying to discover what keeps the record of which devices were connected & if I can clean it of just one device without damaging my regular devices' behaviour.
Closest I can find is How do I make iTunes 'forget' a device in Mavericks? which has some discussion regarding Sync Services - but I'm not sure if that's heading in the right direction.
Also relevant - How can I prevent iPhoto from opening everytime I plug my iPad/iPhone? - which is my eventual aim.