If you're syncing, I'm guessing you probably also have the Mac app. Make yourself a context mode perspective that shows only completed actions, grouped by completion date. Then it is easy to review what actions have been completed today and catch any that shouldn't have been. There may even be such a perspective as part of the standard set on the Mac, I don't recall off the top of my head. In that case, you just need to enable perspectives on the iPhone, which you can do by visiting this link:
http://people.omnigroup.com/kc/Debug...spectives.html