uDraw is a classroom communication system for editing and exchanges of graphics on tablets or notebook computers. There are two main functions: 1) students draw on a blank white space and then upload their drawings to a certain storage place to be displayed in front of the classroom for everyone to see; or 2) students add markings to pre-installed images and then submit their edited images for sharing.
The uDraw teacher page:http://teacher.udraw.mobi
For the time being, the service is available only to teachers and students at The Chinese University of Hong Kong (CUHK). The app will not be useful to the general public.