In the pulpit while I was preaching. I was using my iPhone to control my slideshow when someone called. Luckily (as Calvin would say) it was on vibrate and place on a rubber mat, so no one knew. But it did knock me out of my slideshow control app. So I had to keep preaching while fumbling with the interface to get back to my slideshow. Learned the importance of "airplane mode" that Sunday! :-)