I've recently told my ex's parents more about the extent of his illness. This was well after our break-up and actually following a subsequent break-up for him. He was living by himself for practically the first time in his adult life, isolating, relapsing and having suicidal thoughts. I told his parents in the hopes that they would check in on him more and giving them a heads up as to what they might find. So far it seems like this was a good decision as everyone concerned (myself, the x, his parents) seem at a minimum ok with the fact that I told them. When he was checked in to a hospital after cutting himself about a month ago, I contacted his parents and let them know. I told both him and them that I was doing so more for my well-being than his. I really appreciated the feeling that I didn't have to have such a loyalty to him that it meant the burden of carrying his secrets by myself the way I did when we were spouses.
So yeah, being able to tell on him to his mommy and daddy has helped me. Meanwhile, I don't think it's been unhelpful to any of them.