Doceri

The iPad Doceri app can be used standalone as a whiteboard to generate graphics or screencasts.  When the iPad version of Doceri is used along with a Windows or Mac computer running the desktop version of the software, the iPad can control the desktop computer and annotate whatever appears on the screen.  These annotations are saved in Doceri and can be exported as pdf files.

If you are trying to set up Doceri on a public WiFi network, you will probably need to set up an ad-hoc network between the desktop and iPad.