I am not aware of any solution that can alert you when a certain "non-standard" application is installed.

Is there a particular piece of software you are looking for?  If so, I can see a couple options for you.  You could create a report to run on a schedule and set a policy send you the results on a hourly/daily/week schedule.  The other option would be to use application metering.  You could add unapproved software to the "blacklisted applications" collection and have an email alert sent to you whenever the application was launched.  This would give you an alert that someone tried to launch it which would indicate it was installed.

If you are not looking for a certain application, you would need to have a list of approved applications that you could compare against.  Your report would simply look for machines that include a piece of software not in the approved list:

SELECT c.[Name]
INNER JOIN Inv_AddRemoveProgram ar on ar._resourceGuid = c.Guid and DisplayName NOT IN ('softwareA', 'softwareb', 'softwarec', etc)

You could also create an approved software table to select against like:
INNER JOIN Inv_AddRemoveProgram ar on ar._resourceGuid = c.Guid and DisplayName NOT IN (SELECT DisplayName from tbApprovedSoftware)

Just a couple thoughts.