As many should know by now, BB-8 the spherical droid, is not cgi. The droid is an actual physical object that the actors were able to interact with. BB-8 has been developed with the aid of Sphero the company that developed the smartphone controlled RC ball.
Well Christian Poulsen has already hacked said RC ball into a mini BB-8! If you want to build your own little BB-8, Poulsen has a breakdown on how to make one at Make: