Saurik just released an update to Cycript which brings support for iOS 7 and ARM64 device with tons of new features, almost all of which are now documented in the new manual, on the new website. http://www.cycript.org/
Cycript is an Objective-C/JavaScript hybrid that provides a live console for injecting into existing applications, either on Mac OS X or iOS. However, while developers are often very interested in the tool, it mostly has only been applicable to development on jailbroken devices.
FSM EXCLUSIVE DEAL In the video below, Jay Freeman (saurik) shows off the new version of Cycript that is now fully supported on Mac OS X (all versions from 10.6 through 10.9) and which can easily target the iOS Simulator. Additionally, he explains how this new version of Cycript can be used from Xcode as part of debugging an application “on device”.