I don't have a pace maker...but my wife does.
She was given a considerable collection of literature, including what things to stay away from--and how far away to stay. Computers were not on the list. Contrary to the situation in prior years, microwave ovens are not on the current list, either. The one thing in the house that she has to keep away from (and away in this case means "at least 2 feet") is an induction cooking burner.
Of all the things a Pi puts out, EMF in the kilowatt range isn't one of them. Neither is lots of around 24KHz emissions.
So...Pis are not--in my immediate reading and experience--contra-indicated with pace makers. HOWEVER, this is not medical advice. If your friend is concerned, have the friend ask the cardiologist. If the cardiologist doesn't know, then he can ask the manufacturer.
Also...at least in my wife's case, the pace maker can be interogated and re-programmed non-invasively. I *think* the devices use BT to communicate, but it is very, very difficult to get straight answers from the manufacturer on these sorts of subjects. I should also note that, while the manufaturers own data indicate that some of their software is licensed under GPL, you can't get them to supply or provide a link to the source code of those modules--which puts them in violation of that license. I have not worked up the energy to try Threat of Copyright Suit to shake it loose....yet. (If *I* had the pace maker, I'd insist up front...)