As Leaf seems to be a very successfull news reader on the Mac App Store, we will implement an iOS version as well, but recently we have no timeframe of the project. Follow us on Twitter where we'll inform you about the news.
As long as we do not have an iOS app, we do recommend you to use a sync service (i.e.: Feedly is free) in Leaf. Every sync service has it's iOS client app, and for the more popular once there are several apps that supports them. By using such apps on your iOS devices your articles will always be synced.