Don't get me wrong, I love apps. I have some very favorite ones that I love to use. The reason I say it is not always about the apps is that if you are a BYOD (bring your own device) school, whatever you use should be available on all devices.
Sometimes I think we get so caught up in apps, that we forget to use the camera tool that comes on each device. It is possible to create quality lesson plans for students with a variety of devices. By not getting caught up in a specific app that is designed only for one type of device, you are allowing students to choose what is best for them.
My co-worker and I created a short PBL (problem/project/process based learning) for a BYOD training that I had. It was a PBL for Kindergarten and First Grade about shapes. We had the teachers using the camera tool from their device to scan a QR code with the directions, and then they went around the school to find the shapes their students were studying. When they had at least three images on their device, the teachers put their images into an app that allows them to narrate what the shape is and what the attributes of the shape is. After that, we opened up a whiteboard app for the teachers to create their own shape. They had to record their voice to tell what the shape is and the attributes of the shape.
Yes, I used apps for the above professional development. However, it wasn't device specific.
photo credit: iPad: kids via photopin (license)