Jibbler appears be an enhancement to the iPhone SpringBoard application, the Finder-esque app that acts as a launcher and will support the newly announced 3.0 Spotlight search. Jibbler may be controlled via the iPhone headsetbutton squeezes could be used to record short voice segments from the user, which Jibbler will then interpret. Voice synthesis can then be used to give the user a response, similar to the latest generation iPod shuffle, which can "read" playlists and track namesthe difference being that the iPhone hardware itself could handle real-time voice synthesis.
Ars sources found references to classes and methods named VSSpeechSynthesizer, VSRecognitionSession, SBVoiceControlDisableHandlerActions, SBSensitiveJibblerEnabled, and SBVoiceControlSoundCompletion. Its possible that Apple may allow access to these services via the official SDK.
Its still unknown whether the new voice services will be tied to the expected hardware update in June or whether they will work on current iPhone models.