@Michael Grumbach, several of our teams have created lightweight apps for creating work items in Agile Central from email via the Web Service API, but updating an existing work item is a whole other layer of complexity. I will tell you that we've had Agile Central Technical Services create some integration apps for us to handle full-blown bi-directional sync to things like our Netsuite CRM system and they've been quick and reasonably priced.
That said, if you can live without updating existing work items via integration then Idea Manager is extremely easy to use as your "funnel".