The details of the challenge are described in the document at the link below. Basically students had to work in groups of three or four to create a fictitious news story. There were other criteria as well, including five random words that had to be included in some creative way.
They had only one class period to make the video, including learning how to use iMovie on an iPad. (By the way, my new approach to introducing tools like this is to simply give them the requirements. Once they know what the tools can do, they figure out how to work them on their own.)
You can get a copy of the challenge document in your Google Drive by clicking this link. Change it as necessary to meet your needs. If you share it, please include the link to my blog that's in the footer.
Here's the video that one group produced. On it's own, it's not terribly entertaining. I think they did an excellent job within the constraints of the challenge, though, and they included all the random words (clock, cup, reward, silence and courage). They went slightly over on the 30 second time limit, but I was very happy with their efforts.
(Note that I had already told them my top tips for video projects and they created one video previously using other tools.)