One very interesting application area of grammar engingeering is documentary and descriptive linguistics: Building implemented grammars for languages under active documentation in the field has the potential to facilitate the checking of hypotheses about those languages against larger data samples, and to build infrastructure (e.g. treebanks) to support the next level of inquiry (see Bender et al 2012), as well as raising questions which may well be of interest to the field linguists engaged in the primary descriptive and documentary work. Working on a field language in Ling 567 also has the benefit of the chance to communicate with the field linguist whose materials you are building on.
Below is a list of languages for which appropriate resources exist and the linguists engaged in the documentation of which are interested in having a Matrix-derived, 567-scale grammar built.
For all of these languages, we can have access to digital materials (including text collections and grammars).