This is not a software release, but I spent a few hours plowing through the documentation on Google Wave API, and I'm just noting down how it may be plausible to support LaTeX math equations on Google Wave.
The first aspect is rendering math equation. One essentially makes a Wave Gadget that decides how to turn LaTeX into presentable math equation. There are two possibilities: (1) use the undocumented Google Chart API, but the LaTeX equation length is extremely limited; (2) embed jsMath, and use it for math rendering. The disadvantage of the jsMath approach is that it is rather heavyweight, since each gadget has to run the same jsMath initialization code separately. A third option, which I don't consider a possibility, is to host NTS (a Java implementation of TeX) on AppEngine. The NTS implementation of full TeX stack (TeX to DVI, DVI to image) might be considered heavyweight, but the real challenge would be to workaround its reliance on a real filesystem, which makes it difficult to port to AppEngine sandboxed environment.
Once the rendering part is done, it may be convenient to convert LaTeX code to the rendering gadget on the fly. This can be done using a Wave Robot that listens for document changes and scan for LaTeX code in the blip. I think this is relatively straightforward. However, a concern is that each change requires the robot O(n) time to rescan the whole blip. Editing in Wave would then become noticeably slower as document size grows. This scalability issue must be addressed. I think the current workaround is to have Wave only contact the robot sparingly. This also means robot updates are going to be slow. It may be possible to integrate everything better in the future, by processing update events directly in the Wave Client without using a robot.