I just created a new project using the employee directory sample app. Deployed it as sandbox app and it worked great on my iPhone.
Kudos to the team! This is fun!
As a reply to Mike's question: Yes it works in the sandbox. Just invite the others. I have not tried this yet, but I suppose you could take a picture of the QR code and email it to the other people. They can then scan it from their laptop or PC.
And it so happens that this will be of great use for a new mobile project next week!