SharePoint content database monitoring tools

I found some very good SharePoint Content DB monitoring third party tools.
These are some SharePoint content database monitoring tools to alert administrators if the content database size gets low/full

http://www.manageengine.com/products/applications_manager/database-monitoring.html?gclid=COLs78P4hKgCFUpN4AodZEyzqQ

http://www.logrhythm.com/Applications/DatabaseMonitoring.aspx?_kk=database%20monitoring%20tool&_kt=68cd2851-97fd-4b41-83ff-2b915fccad2b&gclid=CPWJ9MT4hKgCFYLc4Aod_1y8qQ

SharePoint Monitoring Toolkit Executive Overview

http://technet.microsoft.com/en-us/library/bb975149.aspx

SharePoint Monitoring ToolKit for System Center Operations Manager 2007

http://www.microsoft.com/downloads/details.aspx?FamilyId=E4600FD9-F53D-4DED-88BF-6BB1932794F9&displaylang=en