As funny as it sounds the "we get your first born child" clauses in the NDAs are not a rare occurrence. One NDA I was required to sign explicitly stated that every idea or functionality I developed on other projects for up to twelve months after delivery of their project was subject to review by the issuer of the NDA (not even a 3rd party) and that if anything even remotely similar to functionality I will be creating within the new project they're rightful owners of it or that they are able to sue me.