the following code will not compile:

Ptr<MyObject> p;
MakeCallback (&MyObject::MyMethod, p);

The solution probably would require us to define a CallbackTraits<T> template class and specialize it for the Ptr class:

template <typename T>
struct CallbackTraits
{
  typedef T * PointerType;
};

template <>
struct CallbackTraits<Ptr>
{
  typedef Ptr<T> PointerType
};

and use CallbackTraits<T>::PointerType in callback.h wherever we use T *.