A remote control car with Spark core?

I was wondering how it would be possible to build a toy car that I can control with an app on my phone. I know how to build the app, but what would I need to build the toy car with the spark core. What motor would you suggest?

Also, how would I be able to build something that runs with a motor but may be a few pounds heavy? How would be needed to make your the motor can run while holding a heavy object?