Workflowy has its own iOS app.
Here is the link to download:
We're working to add more of the features to the iOS app, as well as documentation.
Here are the basic features.....
The iOS app doesn't have the same hover menu as in the web app. In the iOS app when you click on a line, buttons to Complete, add a note or indent/outdent will appear at the top of the screen. You can also tap an item, hold and drag it to move it. To delete, you need to backspace.