You can check out this app...I haven't used it and may have yearly fee associated with it unless you picked up a cheap android device to run torque.
https://surrealdev.com/gretio/
I'm not sure that it's available for Apple. I only run android and it's on the Google Play store. The car play boxes that we are using connect to the touch screen by tricking it into thinking its an apple device but it's running a version of Android.
The Echo controller is supposed to work as a normal brake controller, the big button is only to manually apply trailer brakes like other hard wired brake controllers. If you lose Bluetooth connection with the controller it is supposed to keep the settings last setup/used before disconnection and...
Can confirm the CUSP unit works found at the below link at amazon.ca
https://www.amazon.ca/gp/aw/d/B09HJCB3M5?ref=ppx_pt2_mob_b_prod_image
I installed the Curt Echo Bluetooth Brake Controller app on it as well as my truck didn't come with the GM brake controller. My trailer is in storage so...
I'm assuming one of the car play boxes like this?
https://www.amazon.ca/gp/aw/d/B09HJCB3M5?ref=ppx_pt2_mob_b_prod_image
It plugs in via USB and let's you run a version of android through Apple car play.