As you probably know, the iPhone doesn't import to-dos from iCal. Even worse, the iPod touch doesn't let you add anything to iCal! But both models allow you to add and modify address book contacts.
It's a total hack, but I'm sure it would be easy to create an address book group named iGTD, and inside of it, contacts named "Inbox", etc. with all your tasks in them.
The idea needs more thought but it's WAY easier than trying to create and run web-app through Safari.
