The Anki OVERDRIVE should not need any introduction. It lets you use your smartphone to control robotic supercars. The Anki OVERDRIVE Big Bang is one of those cars. Big Bang is an armor-plated car with Graviton ore to create massive shockwaves to send your enemies off course. The BF-27, which happens to be a rear-mounted gun, lets you damage anyone behind you. You can also drop explosives on track to damage other supercars around you.
Anki OVERDRIVE is compatible with iOS and Android devices. Sets you back under $50 at this time.