I don't speak for Fair Isaac, but this is my experience with the product.
I have the following kinds of alerts:
1) Name changes. Since everyone seems to have some variant of my (rather complicated) name, I have dozens of these alerts.
2) Address and phone changes.
3) New accounts.
4) Inquiries.
5) Balance increases.
6) New accounts and credit limit changes. (I particularly like the last.)
There's also ones for debt collection and public records, but I don't have any of those.
Sometimes the alerts aren't emailed, but they're always there when you log in. Another advantage of the product is that your TU reports stay around longer (the entire time you have the product, near as I can tell), and changes in your FICO score (for TU only) are summarized in the Alerts screen.
I personally think it's a great value if you're going to want your TU FICO score at least four times a year.