JavaScript Speech-to-Text for blind people

Is it posible to use x-webkit-speech pressing a key?

According to the this post and this post you cannot override the start of speech by clicking the microphone.

What the x-webkit-speech is doing is using the audio capture capabilities of HTML5 and sending the audio to Google's servers for processing, returning the results in JSON. This blogger has reversed engineered it. You could develop a JavaScript library that looks for a key press to start capturing audio on HTML5 enabled browsers and send it to Google's service or to one you have created. The downside to using Google's service is that it is an unsupported API and subject to change at any time. The downside to developing your own service is that it can be expensive to develop and maintain.

Do you know any alternative API (JavaScript)?

This post and this post lists some services available for speech recognition. I did not see Nuance listed. You may be able to use the Dragon Mobile SDK for this. And you may want to check into ISpeech.

Google Translate is very good Text To Speech Engine. I used to read a text with it. For example you have a text: welcome to Stack overflow you can call like this

http://translate.google.com/translate_tts?ie=UTF-8&q=Welcome%20to%20stack%20overflow&tl=en&total=1&idx=0&textlen=23&prev=input

then use browser audio to play it

For speech input you can manual activate listening process, see herehttp://code.google.com/chrome/extensions/experimental.speechInput.html