Since the introduction of Siri along with the iOS 5, there has been a strong number of Cydia tweaks based around voice dictation. In order to use Apple's system-wide voice dictation technology, you need to be in ownership of an iPhone 4S / iPad 3 or newer, but thankfully, the jailbreak quarters are considerably more accommodating. If you like the idea of text being read out by a voiceover software, you may like the Awake Speech tweak, which allows a custom message to be read out after you disable or snooze your alarm.
