How to show the play/stop symbol

Hi all:

I am writing to you because I have an app where I would like to show a play icon when you start recording an activity or a stop icon, similar to what the swimming or bike apps to mention two examples. I guess I need something similar to an overlay but I am a bit lost here. Looking for examples, I saw the AnimationWatchFace, which I guess is of value for what I am looking for.

Do you know of default images and/or which classes I have to use for my purpose?

Thanks,

Javier