BusyToDo can sync task do dates, priority, location, alarms, and associated URLs and notes. It can sort tasks by date, calendar, priority or title, and can filter tasks based on calendar. BusyCal users can also sync repeating tasks and BuysCal tags as well.
BusyToDo for iPhone and iPod touch
BusyToDo requires iOS 4.1 or higher, a MobileMe account, and a Mac running Mac OS X 10.6 or higher along with iCal or BusyCal.
The app is priced at US$4.99 and is available at Apple’s iTunes-based App Store.