Memrise for iPhone or Android device.
Memrise Mobile App can be found on the Apple App Store, Google Play Store, and Amazon App Store.
It is possible to download a course to work on it offline if you have a computer but not internet access
Memrise Team for Mobile
Four man mobile team are building a cross-platform app
Offline mode isn't fully offline, it just uses less data. In the FAQ it says you can turn off mobile data if you want it completely offline though
How to use a Course Offline
You will probably have to save the app for when you know you're going to be without internet for an extended period, rather than try to use the app and the website concurrently.
Memrise iOS link
A fundamental Memrise convention is that stuff in brackets (parentheses) is not tested. In the Android app, on the other hand, the learner has to be provide it all to get an answer correct. This makes some courses hopeless.