BusyMac (a local to Seattle indie shop) recently released their first iPhone app, BusyToDo.

"BusyToDo is a simple, elegant To Do list manager for iOS that syncs tasks with iCal and BusyCal wirelessly through MobileMe. Syncing is automatic and happens in real-time as you make changes on your Mac or iOS device."

Looks good, as are their other apps.