This video is fake (the car often doesn't move when the phone is moved and you just see some blank terminal window on the phone) but in general this is still doable.
Youd just need to control a micro controller with BT (I already did it with an Arduino) and the Arduino can control the car (in my case a bigger real RC car and not a toy) by replacing the original RC reciever. I didn't try it together but bluetooth control via N900 is possible and RC control via Arduino is very easy.