With a little hacking, the gtk front-end of SunPinyin could run on Mac OS X (Intel) now, here is a screenshot:

To build the code, you need install X11 package (available in the 2nd Tiger install DVD), gtk2 (with MacPorts), and a little tricking in configure.ac. You could just use the language model and dictionary files for linux.

Hopefully, we will have a full-porting to Mac. There is a sample on developer.apple.com, about writing a basic input method service. Anyone has interests?

Other references:

1. 现在如何在 Mac OS X 中写一套输入法 (一)
2. 怎樣在 Mac OS X 下寫一套輸入法？（一）（二）（三）