I was more intrigued how this worked than actually getting a whopper since I am not really a fan. It does work, just ate one for a penny.
You need the app and have to sign up with your credid card. App is free. Then you find a McDonald’s and get within 600 feet. From there you order it and drive to burgerking. Luckily both mcd and bk are probably about 1000 foot or less away from each other so it was easy for me. Plus it is next to the grocrery store I was at. For a penny I guess it tasted ok lol