Calls? Or just emergency texts?

The closest thing to what you probably want is the Garmin Forerunner 945 LTE:

https://www.garmin.com/en-US/p/698632

Discontinued, but young for Garmin devices and still available if you're willing to pay irrational amounts of money. It doesn't make audio calls out, but can receive audio messages (to Bluetooth headphones) and send/receive "emergency" text messages either to the Garmin emergency response center (sends a helicopter to your location, if required) or by SMS with a few canned messages or tediously entered custom messages to to a predefined, pre-approved set of emergency contacts, as described here:

https://www.dcrainmaker.com/2021/06/garmin-forerunner-945-de...

I've come across this.

I really would like calling too. There's a lot of daylight between I lost my phone and need to call a cab, and send a helicopter.

Right now I have an LTE smart watch, but the battery is optimistically about 24 hours( on a good day ).

With the Garmin emergency contacts system, you can set up arbitrary messages to send to your emergency contacts. One of mine is "I'm OK, but need you to come pick me up".