Google text to speech
Text to speech for asterisk using Google Translate
requires some perl dependencies I need to install libwww-perl to work.
apt-get install libwww-perl
IBM Watson text to speech
https://github.com/adiazgalache/asterisk-voip
http://stackoverflow.com/questions/38528732/how-to-use-ibm-blumix-watson-speech-to-text-as-speech-engine-on-asterisk
http://platechnotes.patrickarchibald.com/2016/06/asterisk-pbx-and-ibm-watson-text-to.html
https://github.com/watson-developer-cloud/text-to-speech-nodejs
https://www.ibm.com/watson/developercloud/doc/text-to-speech/index.html
apt-get install libav-tools
IBM Watson online demos
https://text-to-speech-demo.mybluemix.net/
https://speech-to-text-demo.mybluemix.net/
Other Links
Twofer Tuesday: Incredible PBX for RasPBX on BeagleBone Black and Raspberry Pi
https://en.wikipedia.org/wiki/Google_Text-to-Speech