How easy wud it be to built one of these.
Any easy or simple solutions.

Needs the voice to be realistic or natural.

 

http://en.wikipedia.org/wiki/Speech_synthesis

http://www.synthtopia.com/content/2009/01/11/free-voice-synthesizer-for-windows/

The wiki article has a list of hardware you can use to build a synthesizer.
The synthtopia is a free download of a software synthesizer/

 

How easy wud it be to built one of these.
Any easy or simple solutions.

I was doing this on my C64 30 years ago.

Needs the voice to be realistic or natural.

There are some good ones out there, but they are expensive. The easy ones are understandable, but not natural.

 

The best way to get "natural" these days is record all the words you want, spoken by a human. Then put it all on a memory card either as individual files or one huge file which is indexed for each word. Cheap memory cards are everywhere at 4Gb or more so its very simple to do.

You can make a phoneme based voice synth with much less memory needed but they always sound a bit 1980's.

 

If you can tolerate a robot-sounding voice, there is this thing:
http://www.sparkfun.com/products/9578

There are examples of how it works on Youtube.

If that isn't good enough then maybe you could use snippets of speech stored as WAV files on a mini SD card--there are playback devices for things like that available. But that wouldn't be true text to speech, and would probably have an artificial sound. True text to speech takes real computer power to do.