OS X Text to Speech apps This may be a broad question, but I think the lack of widespread interest in text-to-speech warrants it:

What are some apps for OS X that do novel things with text-to-speech; i.e., more than just take some text and speak it?

One example might be an app that has a "rewind 30 seconds" feature, or highlights the word currently being spoken in an on-screen document, has a hotkey I can press to "bookmark" the word currently being spoken, etc.
I don't know all of Text-To-Speech programs out there, but I think the current state of this technology is still a little behind.

Only the "standard" sentences, i.e. the most common ones, will be spoken with a good intonation. But in general, more or less, programs will behave like robots when pronouncing words.

Regarding the features you asked, anyway, GhostReader does the job and is actually fairly good at pronouncing. Although I'm not sure about the last thing you asked. The program is commercial but has a trial period. You can download single language packages from the site and load them from the program itself.

I was going to suggest Toau as well, but it doesn't have those features you ask, it's pretty basic. The advantages of this app is that it's free, and the interface is simple. The disadvantage is that it uses the Mac OS X library for language packages. When you want to change a language, it will take you to System Preferences, and you'll choose the language there. This is why it's not my first suggestion, while on the other program, you downloaded specific packages.