Wivik, as far as I am aware, is an onscreen keyboard. It's not really meant to be used as a text-to-speech device. There are free software substitutes available for Windows-based computers.
If you have a Windows Vista or Windows 7 computer, both text-to-speech and speech recognition are already built-in. You simply need a program to access the functionality. Supposedly, the last two versions of Microsoft Word can use this built-in functionality to act as a text to speech program.Haven't met anyone who recommends it.
notme, Proloquo2go is a text-to-speech product for the iPad/iPod/iPhone. It has a big brother called Proloquo for the MacBook and other Mac OS X computers. Be sure and specify that those programs run only on Apple products -- it prevents confusion.
Richard, did you ever try Click-N-Type? It also has word prediction and is free. I especially like some of the special keyboard layouts that they provide and I've been able to add words to its prediction list by simpiy editing a text file.