From the site:
Unity’s game engine allows developers to create, modify and iterate on Wii game functionality with the following features:
- Live Preview: The play button allows developers to instantly preview their game inside the authoring environment exactly as it currently exists, regardless of the development phase. Users can modify any object’s properties and see the results in real-time without pausing.
- Scriptable Controller: Simple, straightforward, fully-featured Wii Remote scripting class lets developers read data from the Wii Remote controller, Nunchuck controller, and Classic Controller effortlessly.
- Optimized Character Animation: Developers can create characters without special exports, imports, or modifications required. Files drop easily into Unity and the characters come to life with full animation on Wii hardware.
- Scriptable Shaders: Unity’s ShaderLab system has been expanded to leverage the full power of the Wii graphics chip. Developers can use one of the built-in shaders optimized for Wii or write their own. They can script and modify any shader on any object.
- Click to Publish: Developers can easily run their game on their Wii development kit, building it with one click.
Read the press release.