I am in the process of trying to figure out a solution for adding webforms to products. The two most important aspects of this is that the forms have to be presented before or at the time that the user is adding the item to the cart -and- the information collected in the form is tied to that particular transaction, such that reports can be run later on. I have already articulated most of the details in this post: http://www.ubercart.org/forum/ideas_and_suggestions/6448/productrelated_...
Anyways, after doing some research, I am thinking that the best way to do this is to make the webform a product feature. Ideally, it would integrate with the current webform module, but that module is more complex than I am going to be able to understand in the time that I have to figure this out.
Could you elaborate a little about the API as it relates to this particular project? I am very open to any ideas of how I might be able to make this work within the next two weeks.