Funny you should say that. Actually, no. That was the first time. And it was a bit crazy ...
My screen capture software (ScreenFlow) capture the entire screen and lets me crop the viewable area after the recording, which I really like. It also allows recording of the screen and one camera, at the same time. It does the picture-in-picture for that part on its own. But I had a third view.
To the left of the what you saw in the video, I had PhotoBooth recording the hardware on the desk. PhotoBooth is a bit nutty in that is records the video flipped horizontally. Pretty dumb, actually. I mean, it makes sense that it should show the preview video flipped, so it feels like a mirror to the subject being recorded. But it's just plain stupid that the recording itself is also flipped. Anyway ...
So then I had to combine the two videos together. Export from ScreenFlow and import into iMove. Use iMove effects to flip the PhotoBooth video the right way around again. Then add it as a picture-in-picture. So far, no big deal.
The real trick was pre-empting that the two videos would need manually synching up, time wise. For that, I started out by putting one, two, then three fingers in the desk cam frame, while saying, "mark one, two, three", a couple times. After removing the audio from the desk cam video import, I was able to sync the ScreenFlow audio with my finger counting.
Then, I noticed that I was advertising the address of the non-secured web app in the iOS video frame. So I needed another picture-in-picture to cover that up. Alas, iMovie does not permit more than one picture-in-picutre! Well, no problem. I just exported the whole video in a lossless format, then imported it as a single file and added the second picture-in-picture to that.
Easy! (if you like convoluted missions and have the time!)
It's almost enough to make me look seriously at Final Cut Pro. {gulp} Ah! Now I $ee their cunning plan!
Oh and, I Blu-tacked my sun glasses in from of the desk cam, to make the LED display photo-expose in a much more pleasant/visible manner. Like I said. Mission! LOL