I gotta say, I'm pretty impressed with its simplicity so far. It's very simple to setup and easy for the invitee(s) to interact with.
Here's the backend...
And on the iPhone...
I will test it a little further before recommending it for anything business related, but it could very well work for coaches and workshop facilitators.
You can download it for the iPhone from the App Store. And it's also available on Apple's iCloud.com service on the Web.
Let me know what you think.