Now that we can jailbreak the iPhone 4S, jailbreak developers can finally use Siri in their tweaks. One such tweak is Lingual which adds language translation to our favorite voice assistant. The tweak, available from the Big Boss repository in Cydia, lets you say "Siri, What is how are you in Spanish" and Siri will respond with "Cómo estás."
The tweak uses the Bing API to handle all the translation requests and, as a result, can support more than 30 languages. It's based on the AssistantExtensions platform and will install that tweak along with Lingual. AssistantExtensions is an architecture that makes it easy to create Siri extensions like Lingual. It's free and has both tutorials and templates to get you started.
If you have a jailbroken iPhone 4S and give Lingual a try, let us know what you think in the comments. I played around with Lingual and it works reasonably well. It's accuracy is based on Bing so the translation sometimes is hit or miss, but the tweak itself is stable.