Almost 8 years later, if you are still looking for Ember App alternative, you might want to take a look at Eagle App. With almost the same feature and purpose to help designers managing assets, offline software, sync with clouds.

https://eagle.cool/

Ember App VS Eagle App full feature comparison -> https://eagle.cool/blog/post/ember-alternative

youre the most welcome

This was an old post, but i'd like to input some feedback as of 2022. Eagle has continue to develop many new features that are suitable for designers. They released 3.0 just last month

Eagle App 3.0 Release Note -> https://en.eagle.cool/blog/post/eagle-3.0

Eagle App Full Review -> https://en.eagle.cool/blog/post/how-to-create-mood-board-for-design-projects

Eagle App development roadmap (update monthly)-> https://trello.com/b/LSsVep1d/eagle-development-roadmap