Here's my understanding. I live in the Apple ecosystem, and don't really know what's going on with Android.

• iPhones don't have incident detection built-in, but the Apple Watch does (disabled by default). I haven't tried turning it on. In theory, you could also enable Siri on the watch and make calls even if you couldn't reach your phone, as long as the phone is in range of the watch, and the watch is in range of your mouth, and you're conscious (or you can get an Apple Watch with cellular and dispense with the phone). Although incident detection could be implemented as a feature in a phone app, none of the major cycling apps have done so. They all do have tracker features, and the iPhone comes with the "Find my" app by default, which lets other people track you if you set them up in advance (my wife checks up on me during my long rides with Find My sometimes). For most of us, cellphones are good enough. When I'm following a route, my phone's GPS is accurate enough to tell if I'm on the wrong side of the road, and cellular coverage is has gotten pretty good, even out in the sticks, depending on what network you're on (I'm on Verizon specifically because they have good coverage in remote areas).
• Satellite trackers like the Spot and Garmin inReach do not have incident detection (AFAICT) but do let you send an SOS message from a remote location where there is no cellular coverage. These are expensive gadgets, and the service plans are also expensive. Your location can be tracked, and some of the fancier ones allow for two-way text communication.
• There's another kind of SOS gadget for use in the wilderness called a "personal locator beacon." These are one-use, "break glass in case of emergency" devices. They do not require any service plan. Also don't have incident detection. More on these and the difference between them and trackers here.