AwesomeQuickMessages cydia tweak provides SMS compose reply from any place.
Note1: a settings icon will be added to SpringBoard
Note2: iMessages from Quick Compose can be sent (for now) only to a telephone number, not to an email address (Quick Reply instead works with all)
Note3: this tweak as been tested only with Latin characters (oriental languages may have some unknown issues)
Note4: Crashes or bad behaviors are caused by the interaction with other tweaks. We cannot grant full compatibility with other tweaks.
Note5: If you reply to an iMessage, all those previously received from the same contact are marked as read. We are working to fix this.