Parking Sensors to Alpine F903D?

Hi All,

I am researching and planning to fit an Alpine F903D Head Unit to an old van I have just bought to pimp it up.

After reading the instruction manual and researching on the net, I have still not been able to ascertain if it is possible to install parking sensors to input into the display of the head unit. The Alpine F903D head unit says that it can connect to parking sensors already installed into a car via a "Vehicle Data Bus Interface", but my car does not already have sensors, I need to install them also.

Can I buy a normal 4 sensor parking aid pack and link it to the head unit or do I have to buy a special pack? Is it even possible to do what I am trying to do?

Is there anyone that could possible help me try and sort this out as I would be very grateful.

Many thanks,

Bren.