Although this seems like a good idea perhaps for huge companies, i believe that replacing human contact with an app, would not do much to promote employee engagement. as an employee i would value personal interaction with HR and my superiors to feel they really care about my well being and retention. A company interface might have the opposite affect.

Now if you are talking about asking non business related questions, like "what's your favorite coffee flavor?" (if next to the coffee ;) )or "what kind of company event would you like best?" - this gives the employee a friendlier atmosphere and engages them as part of team. make it fun and morale building as well as informative for you.
hope this helps!
Duncan