SMS Undo is a tiny app for Nokia S60 devices and iPhone, that runs in the background and allows users to undo an SMS even after hitting Send. It does this by setting a grace period in which users can cancel their text, or go back and edit it.
During the initial set-up, you simply toggle the Undo function to “On” and then set the Undo Timer.
Next time when you write a message, option to cancel it will be available on the same screen itself, and you can also send the message without the countdown by confirming the message.
SMS Undo is available at Nokia Ovi Store for $1.99 (USD), and at Apple App Store for $0.99 (USD).