Anyone out there doing anything with the extended finite element method?

I'm thinking adding core support in the DofMap and FiniteElement classes might be a very useful thing, but curious if anyone had done any work in his direction.

Providing (1) a mechanism for enriching our current finite element bases and (2) a reference level-set discretization in the library for the hyperbolic transport of a signed distance function (probably using DG) could be a very valuable and reusable functionality, I think...