As I mentioned, I use it to send text messages using the termux API. I can type out a text once and use the script to iterate over a list of recipients (adding a 1 second sleep in between so my carrier doesn't block/throttle it). It can also be used to read and respond to messages in an automated fashion, with branching logic based on whatever I want.
I've also used it for other things like automating the downloading/unzipping of audiobooks, pushing photos/videos (or metadata about those) to my web service, and more.
Basically, I use it for whatever I want to automate. I don't think of my phone as an "appliance." To me it's a general-purpose computing machine that conveniently can sit in my pocket and go with me everywhere.
I've never understood why people want to embrace the idea of them as appliances. They are fully capable of being general purpose, they are just (intentionally) limited. Makes me think of a bird (born with wings), where someone intentionally ties the wings down so they can't fly even though they have all the hardware needed for it.