Amazon's TTS support is very limitated: Voiceview supports only english language.
So i ported eSpeak, an open source speech synthesizer (
http://espeak.sourceforge.net/)
You can use it by command line, or you can use a simple kindlet frontend i made for it.
You can speak a free text or a text file, i'm looking for a command line tool to extract text from epub/mobi/azw/kfx/whatev files (if anyone knows please tell me

)
I tested on my PW3 with a cheap usb audio adapter (like
this) and some earphones
Install instructions:
- jailbreak your device

- extract espeak folder from the tar archive and place it in your extensions folder
- copy KSpeak.azw2 kindlet in your documents folder
- connect an usb audio adapter (if kindle says to set your language to english, just ignore it)
hope you enjoy it