Apple Watch complications
The title says it all: there are no "complications" on the first release of the iOS app which really is a shame.
I'd love to see a minimalist complication (ie: a small letter with a badge count for unread mail, in the way Microsoft did it with Outlook complications) which could be added to the watch faces.. It would fix the only negative aspect of an otherwise full-featured and killer apple watch app. You know what you have to do!