Getting an object to follow and object on screen

Hi all,

I think that this is technically possible so maybe someone can help me.

I have a 3D animation where it looks like you are inside a car driving it along a roadou can see other and vehicles driving around you.

What I am trying to achieve is to create some floating labels that appear as soon as you see a vehicle and these actually follow the vehicle as it is driving and only disappear when the vehicle leaves the screen.

Any ideas?

Thanks in advance.

Keith