A tech product I want that does not exist (I think):

A smartwatch with standalone calling/messaging that doubles as a mobile hotspot.

This effectively replaces the phone as a central connectivity hub, so you can leave it at home put a Boox Palma or retro gaming portable in your pocket instead. Or just throw an iPad in your bag and otherwise keep screen time to a minimum. Or switch phones at will without switching SIM cards.

I think this is what the Pebble Core wanted to be, but it never shipped.