Bitcoinmillionaire is built as a cross-platform mobile app using Sencha Touch 2, Compass, SaSS, Django Tastypie and PostgreSQL in a Linux development environment. For the client side code we thought about developing native but came to the conclusion that it is not worth it as we will not heavily use any hardware device features or heavy graphics.
Sencha Touch framework has some disadvantages but it is the best cross-platform mobile app framework on the market. It has a steep learning curve, very bad documentation for newbies and does not support packaging for Linux, but only Windows. As we did not want to use Phonegap/Cordova because it was too much for our needs, we installed Sencha Touch and Sencha Cmd in Windows to build the native app files. Compass/SaSS are used to generate the CSS files for the frontend using mixins. The whole RestAPI which stores the app data is in Tastypie, which is an awesome Django RestAPI framework. Easy to use and very reliable.
There was an idea to use Parse, but that was dropped since it is not flexible, has limitions and requires its own tools/SDK. The development has taken already 8 weeks. It underwent many changes and we had to throw away a lot of code/ideas.
Three biggest mistakes which caused delay were first developing on Localstorage before switching to the RestAPI and second developing in a dummy app folder and then porting all code to the real folder. Third big bummer was trying to work with other engineers on the product who were a complete waste of time either because they were not knowledgeable on the tech stack to deliver any modules or were lazy to work 😉