For Unity3D, Wraps Collider methods as Delegates.

ColliderCallback.cs

using UnityEngine;

public class ColliderCallback : MonoBehaviour {

	public delegate void Enter(Collision other);
	public Enter enter;
	public delegate void Exit(Collision other);
	public Exit exit;
	public delegate void Stay(Collision other);
	public Stay stay;
	void Awake(){
		enter+=DoNothing;
		exit+=DoNothing;
		stay+=DoNothing;
	}
	void OnCollisionEnter(Collision other){
		enter(other);
	}
	void OnCollisionExit(Collision other){
		exit(other);
	}
	void OnCollisionStay(Collision other){
		stay(other);
	}
	void DoNothing(Collision other){}
	
}