[NTG-context] PDF Signature Fields

Hello all, is there currently any mechanism in ConTeXt similar to the LaTeX digsig or eforms package? I want to add a form field that can be digitally signed (which is now already possible with Acrobat Reader, not just with Acrobat Pro). Additionally (like the mentioned eforms package) it would be nice, if you could specify other form fields that should be locked once the signature field is actually signed (according to the PDF spec this is simply set via a dictionary). Anyway: can this currently be achieved with ConTeXt? If not: is there any chance to get that feature added sometime? :-) Best regards Andreas