unit – how to create an activity object with the help of the camera view

good evening, someone knows how to do an activity using the camera view, when the object comes out of the view it turns off when entering active.

I did it with coroutine, but in my project, the fps falls a lot
because of coroutine. wanted to know another different method
I've already used Onbecame and Isvisible, but that's not it because they only work with rendering

the idea would be like that
https://www.youtube.com/watch?v=rlu7HwYhaw4&feature=youtu.be