Ive got my inspiration in Sphero's BB8. Its bluetooth controlled, induction charged, it have battery from an old Iphone 4, H-bridge for motors, charging protection circuit, arduino nano, and boost converter for motors. Battery can last pretty long, up to 3-4 hours of constant driving. Motors are 1:60, but if i would build this again, i would choose at least twice faster ones. It also have reed switch which is directly connected to arduino and bluetooth module reset button. Sphere is clear ornament sphere which i founded on ebay, and body inside is 3d printed. This is second version because i didnt calculated well transmission of wheels inside of sphere corectly in first one so it was so slow. Body inside sphere have separate department for lead weights so that will keep body itself always on wheels. that department, including battery is below wheel axis. Bluetooth is soldered upside for better range. When i finished this project i complitely sealed body so its waterproof.