Product Vision Statement
Sometimes what your team need is the clear vision of the project that is the same for everyone in the team.
One of the best examples of using vision to drive the time was by Mateusz Kwaśniewski. He used the template from Crossing the Chasm by Geoffrey Moore:
For [target customer]Who [statement of the need]The [product name] is a [product category]that [key benefit, compelling reason to buy].Unlike [primary competitive alternative],our product [statement of primary differentiation]
If is fairly simple and restrictive at the same time. The template forces you to think about users and project in different way, and in many situations it proved useful when talking about features, UI and even technology.
You can read more about vision statements at the blog of Cory Foy http://blog.coryfoy.com/2014/01/product-vision-statements-aka-your-elevator-pitch/