I have to develop an app which allows user to speech text, but there are some APIs in the iOS SDK which allow that? Or even third part libs? I have only one problem : the app is in italian language, so a third part lib has to support italian language.
As of iOS 10 (which isn't released at the time of writing), there is a new speech recognition API. It supports over 50 languages and dialects.
If you are looking for a solution, I'd strongly recommend this over a third party library... Apple will keep it up to date, support it, and improve it. You have none of those guarantees with a third party library.
Any UITextField or UITextArea can be dictated using the built-in dictation feature (in devices that support it of course).
An API is not available and you cannot use Siri directly for that.
As of this post there is no way of doing this using native iOS SDK. However, you have the IBM Bluemix Speech-to-Text service available to you for free: http://www.ibm.com/smarterplanet/us/en/ibmwatson/developercloud/speech-to-text.html