Is a custom selection plugin based on user paintbrush input possible?

Hi! I'm a beginner to writing Photoshop plugins and have a quick question to see if what I want to create is even possible.

I want to be able to create my own selection technique that colors pixels based on a users paintbrush input. (The painted pixels would then be used to draw the segmentation.) Can a Photoshop plugin react to an event such as the user drawing on an image? I've done some digging in the SDK and it sounds like this type of plugin falls somewhere in between Selection and Automation, though I'm not quite sure how to proceed.

Does anyone 1) know if this is possible and 2) would be able to point me in the right direction if it is? Thank you so much.

(I'm running Mac Mojave.)