Take a look at the Spot satellite messengers. Various devices with different capabilities. Some you can type messages on the device, others you can configure canned messages that include your location. Does require a subscription but they now have month to month plans so you don’t have to keep it active when not in use. According to their website, a clear view of the sky is required for a signal. I have not used one personally, but an avid overnight hiker I know uses it all the time. Even in areas like the white Mountains in NH. Just know that under thick tree canopy the signal will likely drop out.