Fall detection
Do you have to have GPS + the cellular service on a series 4 watch to use the fall detection feature?
See the reply to:
Do you have to have a Apple Watch with ce… - Apple Community
To use Emergency SOS on an Apple Watch that doesn't have cellular, your iPhone needs to be nearby. If your iPhone isn't nearby, your Apple Watch needs to be connected to a known Wi-Fi network and you must set up Wi-Fi Calling.