torque is a must have app! but you will need a OBD II bluetooth adapter for it to work. They are about £13 on ebay. it will give you live feeds such as boost,throttle position, engine temp, air temp ect. lap times also. but the best future is that it can read fault codes and help you diagnose any problems you might encounter. it can reset the service light too
I have Witness on my iPhone, not sure if it's available on Android but really good for recording your journey, it records the road ahead, time, position speed etc.