Customers like to see progress regularly, it helps them gain confidence in your work and let's them know things are moving forward.
If you can meet your customer face to face, you can easily show them progress of the app running on your own iPhone. Or, you event can send them the app to install ad-hoc on their phone.
If your app isn't quite ready for that, or if time is tight, another option is to send them a video.
Make a Video
.
This screen shows the iPhone simulator running on my own computer. I've set my desktop wallpaper to this cool wood surface. For additional coolness you can draw on a shadow, so it actually looks like the iPhone is sat on a surface.
At Engine Room Apps, we record our videos using Screen Flow, it's a very simple and cool video recording app.
Add Audio
When recording videos for your client, it's useful to record them with an audio commentary. That helps you put the work into context, and point out bugs, or where things can be improved.
Sharing
We export our videos at 50% size, Web-High standard. Because the iPhone is small, we also set a small crop area the video in ScreenFlow. We set it to just the size of the iPhone, with a little room to show some of the desktop. They usually come out under 20MB.
We then upload to Basecamp where customers can download the video. We find it's best to keep videos 2-5 minutes long.