Shopping at CVS? Pretty soon you can just Venmo the drug store.

Usually when you open the Venmo (or PayPal) app, it's to send a payment to another user — like your roommate who ponied up for the pizza delivery. But starting in the fall, you'll be able to use those apps to pay with your phone at CVS Pharmacy stores across the U.S.

Even if you don't have digital payment systems like Apple,...