The only way to effectively set up an alert like that is by using a specially crafted report.
Reports alerts only send something when the report has information. So you could create a report alert that sends one out every minute, as long as the report will only contain info when you need to be alerted.
For example, a report that only shows new assets created in the last 10 minutes. Send the report alert every 10 minutes. If it's empty, nothing happens, but if a new asset was created, you get the alert.