on linux there are more then a few tts engines that you could use but you will need to access them thru a shell comand. not quite what you had in mind I'm sure but it is a workable solution.

Mary TTS has some pretty good voices but is still a bit buggy last time I checked.
ESpeak is ok for a male sounding voice.
FLite does male and female
Festival about the same
SVox Pico (free comercial ?) has a very nice female voice and is used on androids as well, I dont know if other voices can be installed. maybe percused.
there is probable more that I haven't thought of.
using a shell comand I can use them all more or less, and until a better solution comes along that is how I will do it.