Emergency Location Service is part of Google Play Service and does require any special hardware, downloads or updates.
Emergency Location Service is ONLY activated when the user contacts Public Safety Answering Point.
Emergency Location Service computes Geolocation on the Mobile Device and sent to the Public Safety Answering Point via Data SMS (per AML specifications) or HTTPS, which are both open, OS-agnostic protocols.
Emergency Location Service Geolocation is often more accurate and reliable than cell tower IDs.
Public Safety Answering Point or emergency call center), never through Google servers.
Emergency Location Service is part of the Next Generation 9-1-1 initiative.