Cache is actually implemented in a basic form, you need to call $model->addCache() though.
Here are some test-scripts:
It’s not a documented feature and after implementing basic caching I’ve realised that there might be different caching scenarios and I was looking for better solution.
I wouldn’t use addCache just yet and instead implement my own proxy controller to handle transparent saves. That should be relatively easy, see http://book.agiletoolkit.org/controller/data.html.