Although some may disagree with me on this, I would advise against doing any sort of activity just as part of a "premed routine," alone. You do want to gain some experience in the clinical realm, to give you some exposure to the field. . . but as someone pursuing a career in medicine, one would hope you'd be interested in such activities, anyway!
Just choose what you love, what interests you! Take up a hobby you enjoy, meet people, do something that excites you. From my conversations with people during interviews, I believe that what you take away from an experience -- whatever that experience may be -- is what's truly important.