Thanks! I either missed that or it was an update to the post.

When walking around alone in SF, I'm actually irrationally afraid of getting hit by a car and nobody knowing what happened to me. So yeah, if this is what happened that would be terrible and one of my worst nightmares come true.

Well, there are fall detectors out there, both as hardware devices as well as smartphone apps, which can send an SMS automatically in such cases. Of course, they have to be installed a priori.