Ive found task lists without a firm start and end date does not work which is why I add tasks into Google Calendar.

For the 'gadget' I dont think there should be a specific gadget as Google (docs/email/calendar/tasks/talk) has solved the problem of being tied down to a single device.

In saying that I have several netbooks, PCs and iPhones all accessing shared data within the google 'cloud' and I feel effective and productive on each device I use.