Not compatible with iOS7. AE is now open-source so the comunity can help updating it. If you want the maximum number of compatible iOS tweaks on your device, don't update to iOS7 (yet).
AssistantExtensions is an open-source free MobileSubstrate tweak extending Siri (you can open apps by voice, send tweets, turn on/off SBSettings toggles, talk with integrated chatbot and more). It also allows other developers to create their extensions easily. It works only on jailbroken devices (iPhone 4S or older with Spire installed).
I know how important is to support different languages. AE core was designed to handle multiple localizations easily. It supports localization of strings as well as input pattern expressions. Currently all built-in extensions has German language support..
Extensions can very easily react to recognized speech and present a text response. In addition to a simple text response, extensions can also create embedded Apple snippets like Clock, Weather, etc and can also create a brand new, custom snippets with custom graphics. For snippets, the extension loads its resources from a bundle or loads a nib which can be created in XCode's InterfaceBuilder. No private frameworks are needed. There is no limit to what kind of extension you can develop.
Creating extensions is simple. Just follow the quick tutorial, download SiriObjects.h and after a few minutes you will be an extension expert. You can also download theos templates here. After you develop your own extension, you can distribute it yourself or through Cydia - paid or free.
Don't forget that your extension will be loaded into SpringBoard and the snippet class will be created each time the snippet is requested. Therefore make sure your extension doesn't leak memory or crashes. Because when your extension crashes, SpringBoard will crash as well - similarly to SBSettings toggles.
AssistantExtensions is now being developed by community. If you are a developer and want to explore the source code or help improve it, look at the official source release on GitHub.
Logo by @sebhel19 (sebastianhelms.de).