I think most of the things that you envisioned are already covered by the requirements of the FCC

http://www.fcc.gov/guides/wireless-911-services

and

http://www.fcc.gov/guides/voip-and-911-service

There is a FAQ by Verizon concerning these issues at http://support.verizonwireless.com/faqs/Wireless%20Issues/faq_e911_compliance.html

Yours

Karl