CAD-like constraint-based modeling

Coming from the world of CAD I would really like it if constraints were available for modelling. They can be really useful when changing a design but wanting some features to be connected a certain way. The alternative way of doing this without constraints would be to scale every component independently and moving them around until thing look right.

I haven't seen in into any other program (other than point coincident contraint) and I think it would be really useful.