Custom SQL Counter... but on a database level?

Good morning,

I'm looking at trying to find a way to do the following.

For arguements sake, lets say that I have a single table in every database on my server.  This table updates every 5 minutes with a datetime stamp via an SQL Agent task.

If, for any reason, a database becomes more than 15 minutes behind, I would like SQLDM to change the status of the server to "Warning" or "Severe" and, when i hover over it, I'd like it to say "Database X is Y minutes behind".  (Much as we have the alert for Table Fragmentation > 75% on database XYZ")

I know exactly the SQL query I need to do this, however, what I dont know, is how to actually create such an alert? 

Is it possible to create a custom alert on a database level?  (I've seen custom counters, but that only seems to be a single, numerical value at a server level)

Thanks

Andy