Sorry if I missed the obvious, but I've googled up and down the problem without any success.

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Task:
I need to ensure to perform some data integrity check/update/erasing whenever unmounting a particular device (it's "shall" be in a consistent state, but it's not a hostile environment, so the approach is robust enough - I cannot do this after mount, since the consistency is relevant to a 3rd system)

Approach:
The simple way to do that for umount is a udev rule that "fixes" the mount_options to uhelper=my_integrity_check, where the helper is a simple script which checks and does the relevant things and then calls "umount -i"

Problem:
The problem are the GUI tools which invoke udisks2 via dbus to umount the device what apparently (didn't really check what happens) calls /sbin/umount.udisks2 directly - not even an fstab entry (which i'd like to avoid) could prevent that "removing safely" happily ignores the uhelper entry.

Suggested solution:
So, what would be could was if either the udisks daemon would check and invoke the uhelper option or (might even be better) would allow me to configure or unconditionally invoke a local script to perform this custom clean-up.
(Bonus points for vendor/id/system matching, but I can completely detect the relevant device from userspace.