what do i need to buy to get rear view camera on Pioneer SPH-DA120
 

what do i need to buy to get rear view camera on Pioneer SPH-DA120? is there a harness i can buy so that everything is plug and play?

I don't think you need anything. your head unit should have the yellow video plug in the back. the stock ones needed a harness because they didn't. you just need a reverse trigger (not sure if your aftermarket HU had it transferred over, but the stock BRZ already had it wired in) and tap into a power source + ground.