You can now use co-worker tags to set up a system for approval and review of hours. To set this up, go to a co-worker you want to set as responsible for reviewing/approving hours. Go to the co-workers main page, click edit:
Then add the co-worker tag that you want to be set on each co-worker.
This means that when you define a co-worker tag. The person responsible for approving and reviewing these hours can go to "My pages > Project Management > Hours report"
The hours available in the report will include all the co-workers for the tags defined in the responsible person's profile.