An interesting problem today. A SP List is being used to track responses to an invitation. For this event, an entry only needs to be created if the invitee wishes to attend, so the only required field is the name. The typical list processing is a bit overkill, since typing the name is not really necessary, and the the Attending field is always yes.

It seems that I need to wrap a call to the web service or object model. There is no built-in RPC method to insert/update a list item.