Neither of those are quite right. You could say: I do what concerns you or I do what interests you But they don't make a whole lot of sense. Concern and interest are not the same thing and cannot be used interchangeably! Concern means to worry about something or someone, or to relate to something or someone. For example: This concern's (is about) a friend of mine. or I am concerned(worried or anxious) about the outcome. Interest is when you want to learn or know about something or someone. Examples: You are interested in learning more about this book. Or She developed an interest in swimming.

Interest and Concern have a similar meaning. Though, Interest means something you Like or something you Want, like a Game. I am interested in Games. Concern means something that bothers you, something Bad, like Bills or Finances. I am concerned by Money.