how would the crew contact Medlink in-flight?
You could also patch through VHF with a DTMF microphone which up until a few months ago, that's how the airline I work for contacted MedLink. However, it takes the one pilot completely out of the equation with the back and forth conversations with the Flight Attendants, never mind waiting for the frequency to clear up so you can use the thing to only then figure out you've travelled 100 miles and now need to switch to another frequency.