Unread is a tweak available since last evening in Cydia, and with its help we can quickly mark any conversations present in the Messages application of our iDevices. The tweak was designed with the idea of allowing us to mark as read/unread any of the conversations present in the Messages application, in this way we can ignore messages that we don't want to open, or mark as unread conversations on which we want to read again.
Hold on any conversation in Messages to mark it as unread (or read, if it's already marked). No options to configure. Only tested on iOS 7, but may work on older versions.
Unread is available for free in Cydia's BigBoss repo.
