I have done a similar thing with SSIS, you just need to add the new monitored instance into a table in your repository and ensure the account running the package has permission on the target Instances. I then have 3 packages, one that runs stat's daily, one that runs hourly and one that checks status, agent heart beat, PLE etc every 5 minutes. I then have a aspx page looking at the repository for status info and some reporting services reports pulling of trend graphs etc.

I beleive i got the original SSIS packages from a feature on this site and modified it to add more metrics and update the code for SQL 2008 instances.