Implementing PsiLanguageInjectionHost

As usual ;). I want to embed HTML in my language (not vice versa).
Now I can inject some language constructs to existing PsiLanguageInjectionHost implementations. These are PsiCommentImpl, PsiLiteralExpressionImpl, XmlAttributeValueImpl and XmlTextImpl. But I want to embed HTML (I wish it could be embedded with javascript support) in my own PsiElement type.
The javadoc for PsiLanguageInjectionHost says, that I don't have to implement PsiLanguageInjectionHost by myself, unless I want to inject something into my own custom PSI. That's the case. I'm willing to implement, but how? You have no open implementations of PsiLanguageInjectionHost - how do I learn by example?
Can you give some instructions on how to implement the sweet PsiLanguageInjectionHost interface?