View issues without an estimate

One of the requirements in our project is that all issues need to be estimated. Accordingly, there are two things I would like to be able to do:

1. Create a filter for "Tasks Needing Estimates" so that users can login and periodically look at tasks assigned to them that still require an estimate. Then they could quickly click through each and assign the time estimate.

2. Ability to set a few rules regarding time estimates, the most important of which is, developers cannot start work on a project until the estimate has been filled in.