I've been working on a open source OS X app called chatta in my free time. chatta uses Google Talk when your friends are online to send them instant messages and Google Voice when they are offline to send them text messages. It handles all the switching and merging for you, you just message.

Both the App and the library that backs it, ChattaKit, are open source and you can check them out on github:

https://www.github.com/crazyideas/chattakit https://www.github.com/crazyideas/chatta-osx

It's still an early beta, so it's quite bare bones and I have lots of UI sprucing up to do, bug fixes, and of course additional fancy features to add. That being said, I'd love some feedback from the HN community and to see if their is any interest in an app like this.

You can download it from: https://github.com/downloads/crazyideas/chatta-osx/chatta-osx-beta2.zip

Requires OS X 10.7+ (Lion or Mountain Lion)

Warning: As with all beta software, this may destroy all your data and/or kill your cat. Use at your own peril.

Thanks!