edit: I just watched the Notes Plus for iOS video... gen.paper seems similar, but with a slightly different feature set. It won't automatically convert a sketched shape to a vector drawing, but it does give you tools (ruler, protractor, compass) that are pretty flexible and useful. Plus, the background looks like notebook paper... your choice of ruled, isometric, cartesian graph, or music staff.
(I am just a gen.paper user... I have no connection to the developer.)
Last edited by ibillwilson; 12-06-11 at 08:57 AM.
Reason: additional info