With the way I see libraries using automatic item modifications, a report that is emailed would be preferred.  Typically they are using this function to move things from "New" to regular shelves, and need a list of items to physically take off the New shelf.  So an emailed report with call number, title, and barcode would be very helpful.  We get a LOT of requests for this!

Other crons generate a log file, so I'd stick with that standard. One could then set something up on the server to email a copy of that log file.
I've poked a this a bit a little already, so I've assigned this bug to myself. But I'm unlikely to get it done really quickly, so I might not be a great option if there's urgency here.
I'm thinking something similar to items.content would be nice -- a set list of fields that are provided per updated item with the ability to customize that field list if desired.

Also, I should add, this cron already has a log option, it's just not very helpful. It gives an itemnumber and the new value of the edited field.

Using action logs seems like the most flexible option, as the results could be emailed with run_report.pl, right?

Changes made by the cron are recorded in the action log, flagged as performed by user 0 via interface cron. One could write a report to list those and schedule it to email to the library.

However, see bug 20101 -- the cron log doesn't record that the cron was run. This is really a separate issue, but came up in conversation about this. Looks like Kyle had a patch for that bug nearly complete?

Automatic item modification by age does have a verbose mode and that output can be emailed - it's just not built into the job to send the output anywhere, nor is it configurable as to what information is sent.

I suppose this should be logged as interface cron and item modification in the action logs. I haven't tested, but if that was the case, I think we could mark this closed?