The problem with generalizing about publishers is that you can't generalize about publishers. Big or small, they are all uniquely crazy.
I don't mean that as a bad thing. They have to be a bit crazy. Sane people pick easier industries to work in.
I'm not going to go into specific implementation tactics. The options at the moment are very limited. You can do simple audio and video on most e-reader platforms but for anything more than that you either need to go proprietary (.ibooks), online (a website) or native (iOS or Android app).
This will change in the future but exactly how, we don't know.
Ignoring the technical side (yeah, I know, that's ignoring a lot) the problem with interactivity can be broadly broken down into three areas:
1. Extending existing titles.
2. Re-appropriating existing material.
3. Original works.