Tweetmarks is a web service for setting and getting the “last read” tweet for a given Twitter user. It can be used to “sync” the reading position between multiple Twitter clients and platforms.
I’d love if many Twitter clients integrated this.
Unfortunately, I doubt that Twitter’s official Mac and iOS apps will. Twitter has decided, for whatever reason, not to do this to date. I heard a while back that this was because they want people to just read what’s there now, like a river of news, not to try to “keep up” with a potentially insurmountable timeline. They didn’t want to encourage features like this that would allow someone to know how far “behind” they are, because that could cause guilt and feelings of information overload, which could discourage usage. (For many of the same reasons, I don’t display “unread count” badges anywhere on Instapaper.)
But the official Twitter apps all have those blue “unread” dots, which function very poorly without unread-status syncing. Each app is great if it’s the only one you use, but if you try to use, say, the iPhone and iPad clients, this problem can annoy you every day.
Maybe Twitter will add unread-status sync to the API someday, but I doubt it.
And as long as Twitter doesn’t have an API for it, widespread Tweetmarks support in apps is badly needed for anyone who uses multiple Twitter clients. So if you make a Twitter client, please add Tweetmarks support.