SiriToggles Cydia tweak enables iPhone 4S users to control brightness, app launching, shutting down their iDevice, toggle system settings including wi-fi, bluetooth, cellular data etc. integrating with Siri.
See also:
Jailbreak iPhone 4S with Absinthe
Jailbreak iPhone 4 S with Command Line Interface Corona
AssistantExtensions Send Tweets, Search YouTube, Open Apps etc. through Siri
Sireet Cydia Tweak Uses Siri to Send Tweets from iPhone 4S
Lingual Cydia Tweak Translates Text Using Siri into 30 Languages
SiriToggles also works for any iDevice older than iPhone 4S having Siri port.
You can download SiriToggles for iPhone 4S free through Cydia under BigBoss repo.