Wilderness, austere, and disaster medicine are also available to IM/FP/Peds and don't really lead to jobs anyway. I mean I don't doubt there is one guy who got a job off of those fellowships but mostly it seems to land you unpaid positions on committees. They're either hobby degrees or scams, depending on how they're structured.
Non-ortho sports is arguably the most oversaturated field in medicine and is, again, available to IM/Peds/FM. Everyone I know who did this fellowship was able to practice part time at best even coming from the much lower compensated worlds of FM and Peds. I have never seen an ER doctor do it at all.
For an EM doctor EMS, hyperbarics, Ultrasound, and Peds EM are usually skill set expanders. They make you a better doctor but they don't usually change your practice environment, other than being a selling point for a position in academic medicine. Again, I am sure there is at least one guy who is full time hyperbaric medicine, or whatever, but it is not common
That leaves four fellowships that are really ways out of EM: Critical care, pain medicine, palliative care, and toxicology. Tox and palliative involve giant pay cuts, so that really leaves with you with critical care and pain.
So my point was that if you hate hospitalist IM there are a huge array of fellowships leading to a huge variety of practice environments with higher salaries, and for that matter you can move into a number of practice environments very different than hospitalist without even doing a fellowship. With EM you're mostly stuck with EM. Or pain. Or critical care. I should have also mentioned critical care.