A remote can have multiple url entries. 'git push origin master' in my case pushes to Bitbucket, then GitHub. Must be manually added through 'git config -e' though. The order is important as it pulls from the first remote URL, while the push is to all.
What i mean was for a web service that would monitor changes on public repos (commits, tags, branches) and would sync them automatically (mapping accounts, pruning branches, etc).