Tonight, as I was driving, I was thinking about how it might be good if I could automate toggling do-not-disturb mode on my phone when I was in the car by the state of the “detected activity” sensor. This way I wouldn’t get bothered by non critical notifications while driving.
Is this sort of thing even possible with home assistant?
Yep, you can send commands via notifications:
This is outstanding. The more I dig into it, the more impressed I amm with Home Assistant - and now the Home Assistant App as well does this? 
This did the trick for me. I have yet to test this out while driving, but here’s the bones of the automation.
I have plans to make this into a blueprint so that my wife can use it as well, but it’s just for me for now. I’d need parameters for the phone detected activity sensor, a helper for caching the value of the sensor, and the name of the notify service for the phone.
alias: steve_dnd_while_driving
description: "Enable Do-Not-Disturb mode while driving"
trigger:
- platform: state
entity_id:
- sensor.steve_galaxy_s23_detected_activity
to: in_vehicle
id: driving
- platform: state
entity_id:
- sensor.steve_galaxy_s23_detected_activity
id: not_driving
from: in_vehicle
for:
hours: 0
minutes: 2
seconds: 0
condition: []
action:
- choose:
- conditions:
- condition: template
value_template: "{{ trigger.id == 'driving' }}"
alias: "sensor detected driving activity"
- condition: state
entity_id: sensor.steve_galaxy_s23_do_not_disturb_sensor
state: "off"
sequence:
- service: input_text.set_value
target:
entity_id: input_text.steve_do_not_disturb
data:
value: "{{ states('sensor.steve_galaxy_s23_do_not_disturb_sensor') }}"
alias: "Save previous value of do-not-disturb sensor"
- service: notify.steve
data:
message: command_dnd
data:
command: priority_only
alias: "Set do-not-disturb to Priority Only"
alias: We're driving
- conditions:
- condition: template
value_template: "{{ trigger.id == 'not_driving' }}"
- condition: not
conditions:
- condition: state
entity_id: input_text.steve_do_not_disturb
state: ""
alias: "Saved value of do-not-disturb is not empty"
sequence:
- alias: Set do-not-disturb to 'off'
service: notify.steve
data:
message: command_dnd
data:
command: "{{ states('input_text.steve_do_not_disturb') }}"
- service: input_text.set_value
target:
entity_id: input_text.steve_do_not_disturb
data:
value: ""
alias: "Clear saved do-not-disturb value"
alias: We've stopped driving
mode: queued
max: 10