ImmediateSend is a tweak launched last night in Cydia, and with its help we can send messages from anywhere in iOS. The tweak was specially designed to allow us to respond to received messages without opening the Messages application, it works in LockScreen/Springboard/Notifications Center or in any iOS application. The tweak is capable of sending both SMS and iMessage messages, all depending on how we have organized our contacts.
ImmediateSend enables you to send SMS/iMessage immediately in Lock Screen/Notification Center/Banner/Alert/Contacts/MobilePhone, without having to open the SMS app and wait until it fully launches. This tweak auto detects if the address you're texting to can receive iMessage and shows you two different kinds of reply dialogs accordingly. After writing back, the message will be marked as read, so it won't disturb anymore. Another important feature is that when you text a person from Contacts/MobilePhone, you can choose to send an SMS or iMessage.
The tweak works only with iPhone terminals and only on iOS 5, and in the Settings application you have a menu where you can configure its settings. ImmediateSend is available for $0.99 in Cydia's BigBoss repo.
