I sometimes travel with a family member who has a pacemaker.

They just walk over to the whole body scanner (where you put your hands over your head) and go through there. If the scanner is closed, a TSA agent will come over and open it for them to use. No need to show any type of id card. A pretty simple process, but my relative does have to have further screening with a wand or pat down of a specific area about 1/3 of the time. They don't seem to mind. I guess it is better than having something possibly cause problems with their pacemaker.

As to their carry on, they would have the same visibility of it as they would if they were in the regular line, with the exception of the few seconds when they are actually being scanned in the machine.