I am the author of the Date iCal module, and the new major version I'm working on (3.x) requires a two-part schema update for users who had 2.x installed. I've written the update hook that makes these changes, but if one of my users fails to run the database update script, they will get an error message relating to their iCal feeds importers.
The right solution is for them to run the update script... but if they just go in and manually change their importers to get rid of the message, their importers will remain permanently broken (because the second part of the schema update won't have been executed).
So is there any way to display a message to users who haven't run the update? Or somehow forcibly execute the update hook the first time a page load occurs when 3.x gets installed overtop of 2.x?