Looking for an automatic update plugin

I have an interesting problem and am looking more for advice than a troubleshooting solution.

I have multiple blogs (and wordpress installations) on subdomains. I would like to find a plugin that will automatically create a post on my mainpage when a subdomain updates with a link to the post in the subdomain.

Is this possible to do? Is there a plugin for it? Or perhaps can I use another plugin to creatively solve this problem?

Any suggestions would be very appreciated!