I also realize your point where Uber has its own app, it's not like a phone number you just call. So a "vibration input" type device or something small/maybe without a screen would have to deal with that problem too. Voice would be the easiest interface to talk to an otherwise brick.
I don't know, was saying it generally like Apple watch seems to be an extension of the iPhone
Not sure if it's still a thing but I remember being able to call Uber with my Apple Watch (cellular version) in 2017 when my phone died.
I also realize your point where Uber has its own app, it's not like a phone number you just call. So a "vibration input" type device or something small/maybe without a screen would have to deal with that problem too. Voice would be the easiest interface to talk to an otherwise brick.