Lifehacker had an article on doing that in a crockpot
http://m.lifehacker.com/5941290/make-a-no-fuss-caramel-dip-with-a-can-of-condensed-milk-and-a-crock-pot
Have you ever had it? When I was a child, my mom would make it and then chill it, open both ends of the can and push it out, serve a slice cut off with milk on it. That is how my son likes it. I have not made any in several years. We never used it in any recipes, just ate it plain or with milk on it. It would be great to spread on apple slices.
An even easier, safer version invented by a chef——pour the condensed milk in a Mason canning jar.
Place the jar in boiling water-—boil away til the condensed milk turns to caramel.