Explain Everything is a sophisticated screencasting app for the iPad. It is a full featured app that doesn't require any account. The app costs $2.99 but is well worth the price.
This program has many features useful in screencasting: upload photos from gallery, add arrows, use a pointer, add text and sound. Great tool for making tutorials or having students demonstrate their understanding of concepts.
Videos can be stored locally on your device as well as being shared with a number of cloud based storage programs such as DropBox. Videos can also be directly uploaded to YouTube which is a great feature.