DOCOMO's Text to Speech API accepts inputted text in English, Katakana or Hiragana, and translates this into a natural sounding spoken voice. The API can be integrated into a Java application using the DOCOMO Text to Speech Java SDK.
If it's speech-to-text services you're after, Vocapia Research is in the game, offering a variety of speech technology services and working with their clients to adapt, fine tune or create products that are relevant for specific applications. One of Vocapia's products is the VoxSigma speech-to-text software suite that is suitable for many languages and a variety of audio data types. The VoxSigma API is available as a Web service via a REST API over HTTPS.