(2013-07-15) Taco Task Hub
Taco is an Issue Tracker hub/integrator: See all your tasks in one place, from the services you already use (like GoogleTasks, GitHub, BaseCamp, ZenDesk, and RSS). Work on what matters. They raised $7k on KickStarter to support building additional connectors (Trello, Asana)
They charge $7/mo/user.
Sept'2013: confirming the decision not to have native tasks, or even a native interface for creating/changing tasks in the underlying stores.
Jan'2014: up to 40 connectors.
Jun'2021: they still exist!