There are existing fairly-good mechanisms for people looking to network whose primary criteria is shared religion (shared absence of religion has somewhat weaker tools in many locations, and I suppose a tool focusing specifically on that audience might be valuable.)

So, while religious filtering might be of some importance to some users of a new friend-finder tool, there are, I think, fairly good reasons to think that the people for whom it is most important are exactly the people that don't need a new tool at all -- people who network through their religious communities.