annoyedGet his or her phone number, then go to an Apple Store and call it from one of the iPhones on display.
Because the thing is so intuitive and insanely easy for someone trying it out to find the recent numbers called, the phone number owner will receive random texts and phone calls for the next several days, or at least until Apple employees reset the phones to the in-store display settings.
For extra bonus lulz, try it with your own number, but only if you're not smart enough (1) to realize until days later that this explains all of the stupid texts and prank calls you've been receiving, or (2) to have initially figured out that this is exactly what would happen if you called your own number from the damn thing.
