Doceri is a remote-control app that lets you do whiteboard-style presentations, including PowerPoint and Keynote slideshows, with real-time annotations on an iPad. It consists of two components: an iPad app, and software for your Mac or Windows PC. Doceri enables the iPad to function as a wireless remote. Using the touchscreen, you have full mouse and keyboard control of your computer.
The app's annotation mode, used in conjunction with the optional $39 Doceri GoodPoint stylus, lets you mark up, highlight, and add text. Whatever you draw on the iPad's display appears on your computer's screen too.