iPhone app ideas made with the app developer's sketchbook

I created the app developer's sketchbook, but I also use the sketchbook to lay out my iphone app concepts. Over the next few weeks I hope to share several of my app ideas with the world, and hopefully receive some level of feedback as to the app concept quality. I would not be surprised if these applications exist for the iPhone with the explosion of apps available. So, let me know if my iPhone concepts hold weight, or if I'm completely full of shit.