For manual deployment, the single iojs binary and your project folder should suffice, along with a way to start/restart your app automatically.
EDIT: To clarify, though I haven't tried it myself, it looks like you can just specify `"engine.iojs": "1.0.0"` in your package.json, and Heroku will install the entire io.js system for you.
For manual deployment, the single iojs binary and your project folder should suffice, along with a way to start/restart your app automatically.