We’ve used Allianz for years. We need good medical/medivac during our 5 - 6 month stays, and their coverages are great ($50k medical/$1 mil medivac). We’ve had two separate medical emergencies and the reps took over the cases immediately. In fact our initial out of pocket expenses were reimbursed the next morning I was in the hospital. That’s because the medical/medivac/repatriation coverages are PRIMARY, that is important. Be aware that even with Primary coverage you need access to cash (credit/debit) for initial expenses in an emergency.

There are also insurers who specialize in medivac coverages like MedJet. But Allianz has been excellent and we cannot recommend them enough. Great coverage for the price! The insurance is good for up to 6 months. I used to purchase our trip insurance through the insuremytrip.com site, but that site doesn’t always include some of the best insurance policies so do your own research too. I just go directly to the Allianz site. Also great trip cancellation/interruption/delay coverages of course.
We’ve used other insurers like Nationwide, there are several highly-regarded insurers, Primary med coverages is just critical. Of course even with Primary coverages in most cases you usually still need to submit a claim after the event and get reimbursed. But in the event of a 2-night or longer hospital stay, or a medivac situation the insurer will step in and take over the case once the patient signs off…