There's some work in this area already, e.g. https://www.goodsamapp.org/.

gregsadetsky · on June 18, 2018

Thanks for the link. I think that this needs to be on mobile OS level to be effective. The good news is that there are only 2 major ones.

See https://crisisresponse.google/emergencylocationservice/ and the 112 (the EU’s 911) work on AML. That service, piggybacking on SMS to send location, is supported by both Android and iOS but is only available in a few countries.