I don't know whether you have access to the "Taptic Engine" API on iOS, but a tactile ping when striking the ball and thuds when it hits a planet surfaces could be nice.
That is a nice idea indeed. I'll have to look into it. I'm always a bit concerned about vibration in games since you don't know how intense it will be on different devices: it can be very tacky if it is over-the-top.
