Analogue proximity trigger

Hi all,
I’m trying to get my head around a problem. I need to create a proximity sensor, for an analogue state. For example, those reversing alarms on cars that have a beep that gets faster the closer you are to an object. I have got it working with multiple sphere colliders, each triggering a different collision, but I would much rather it be an analogue trigger - so a single volume that can increase a variable by 0.01 per second at the edge, and 0.1 per second at the centre. Two questions -

  1. is this possible?
  2. if this is not possible, is there any way other than multiple colliders on the actor?

At this point, I’m only looking at the collider being on the actor - not on the trigger object - but I have no issue with doing it on that instead.
Thanks for reading!