What iOS api is used to put a colourful countdown timer in the Lock Screen notification area?

Question

When you have an active timer in the Apple clock app, it displays the countdown as a colourful interactive widget in the notifications area of the Lock Screen.

I know that it used to be the case that Apple's clock app used a private API to put a countdown on the lock screen, and third-party apps could not achieve the same result.

However I've just seen a parking app (RingGo) showing what looks like a custom-designed animated countdown interface on the Lock Screen. I didn't have to add it to my Lock Screen as I would a WidgetKit widget.

What API is RingGo using to do this?

Apple's native timer:

RingGo app:

Answer 1

It's the Live Activity API.

Thanks to Andrew in the above comment for the info.