Resident apple nerd here. My friend sent me this thread in hopes that I might be able to help. The series 4 watch is programmed (but you must turn on this feature, it’s not automatically enabled) to detect several types of falls.
When a fall is detected, it will play an alarm (even if the watch is on silent) prompting you to answer if you’ve fallen or not. If you do not answer within a certain amount of time and it determines you have not moved from the fall In that time, the watch will automatically call emergency services for you. (It will also alert your emergency contacts that you’ve contacted emergency services as well, but you must have a medical ID set up in the health app with the emergency contacts info at bare minimum).
Apple states that the watch cannot detect ALL falls, and that certain high impact sports might trigger this alert without even falling. However, I have yet to set mine off riding, but it did detect when I tripped and fell over my dog a couple weeks back. So there’s that. I think the watch would be set off more by someone doing kickboxing, karate, or something along those lines versus riding, but I haven’t tested that theory.
I personally upgraded from the series 2 to the series 4 with cellular because I’m disabled and figured that it would be a good thing to have in case of a fall. Just be mindful that a watch without cellular (the gps only model) must be within Bluetooth range of the phone to make/recieve calls and get notifications. The cellular can only activate on the four main carriers (sprint, Verizon, att, and T Moblile) and a couple within Canada.
If you you have any more questions, feel free to ask away!