I absolutely wish this was available to everyone, given the patient has no chance of recovery and has specified that this is what they want in some form or another.
I'm typing this as I sit next to my great aunt as she lies on what will soon be her deathbed. She was diagnosed with lung cancer a few years ago, and she opted to not undergo treatment under the opinion that she would not survive it (she was 89 at the time of diagnosis). In the past week her health has gotten so bad that our original plan of putting her in long term care was originally changed to having to put her into hospice because her health would not allow otherwise. The day after this change we were informed that she would probably never leave the hospital.
When I got to the hospital four days ago she grabbed my hand and begged for me to help her, telling me that she just couldn't take it anymore and that her pain was too severe. In response to this the doctors began to heavily sedate and medicate her so that she can just sleep and hopefully not feel the pain. I say hopefully because she has since lost the ability to enter a state of consciousness beyond babbling gibberish, leaving her unable to communicate with the doctors regarding what to do with what time she has left. Her doctors have talked enough to her about her wishes over the past few years, and we have all agreed that her comfort should be the top priority. She has been taken off her medication beyond the pain killers and her sedatives, and her oxygen supply has also been lowered to the minimum amount possible. This decision was made with the hope that it would let her pass away comfortably and quickly. This has not been the case.
The things that I have seen her go through in the past few days I would not wish on my worst enemy. For example, today her kidneys started to fail so now parts of her body are swelling because fluids have nowhere to go. I would not allow my dog to go through this, yet here I sit watching her die a very slow and, based on her lucid reaction, at times an excruciatingly painful death. At her prime she was one of the most full of life people I will ever have the pleasure of knowing, and there is no way that she would want to go out like this. Given the choice we would have absolutely allowed her mercy and the option to go out with some dignity. Instead I've been going to bed the last few nights hoping that we'll get the call from the hospital, only to hear nothing and go back the next morning to watch her suffer more.