Current work in progress for the offline HTML5 hybrid app, please try it: https://checkvist.com/auth/mobile
We also have a separate feature pool for it:
I have to say, too, that not having a native android app is why I am not using checkvist. I love the interface and it has views that no other task list manager has. At this point I am not going to use checkvist because there is no native Android app, but will check back once and a while.