We desperately need a high quality open-source Firebase/Simperium/Spire. A simple, robust, realtime data synchronization layer with libraries for major platforms. These projects all look great, but outsourcing this infrastructure is simply not feasible for lots of projects.
ShareJS is a good example. However I don't think this is the right approach necessarily. The FireBase API is a lot simpler and in casual tests it's much faster too.