BytaFont 3 is
now updated for iOS 9 which allows you to change the font style of your iPhone,
iPod Touch & iPad.
Here is the full change log for
BytaFont 3:
  • Swap Mode for iOS 9
  • New weights supported in Tweak Mode:
    Semibold, Heavy, and Black
  • Cydget support has been dropped: to
    customize the Lock screen you may use the Tweak Mode
BytaFont 3 tweak is available in Cydia via the ModMyi Repo for
free and is compatible with iOS 9 or higher. 
If your device has not yet
jailbroken, then follow this step by step guide to to jailbreak iOS 9.0.2 untethered by Pangu.