A while ago I bought a document camera costing about $700, a really useful device to replace the overhead projector. A document camera can be used to capture an image and project the image onto a large screen.
Then I bought a VGA connector to connect my iPad to a data projector or any other screen or monitor, and for just $30 my iPad became a portable document camera with a heap of extra functions.
Secure the iPad to a small tripod / retort stand to keep it stable. Then select the camera icon to use the the camera function to project and share any image.
There are fantastic ways to use this in education, for example if you are doing a dissection, you can capture the image and project it for the class to view. You can capture images of objects and plants for science experiments. You can even demonstrate mathematical concepts using concrete manipulative.
I would love to hear how you are using this function in your teaching.