Some of you remember my Application for WM5 smartphones. The application contained SC1000 and CR1000 sets and helped me a lot to get 40V as for non-English speaker. Many hours of using the application and changing it on everyday basis led to a pretty powerful and usable preparation tool. Unfortunately, GMAC banned 1000 series and the application became history. However, I have own experience what works and what doesn't for mobile device preparation tool. There are my thoughts:
1) The shortest educational cycle - 1 problem. The power of mobile applications consists in possibility of spending every free minute on preparation. If we look at our whole day, it will be difficult to find 75 minutes. Moreover, to be concentrated over whole educational cycle (whole test, verbal or quantitative parts, quizzes), we have to study in silence, don't we? But what if we have only 5 minutes, let's say in cafe, another 5 minutes waiting a friend or appointment and so on? I found the most appropriate modes of working with mobile app: A) problem -> answer -> (+ bookmarks if I think it would be useful for me to analyze the problem deeper) --> next problem. B) problem in bookmarks -> explanation -> (- bookmarks if I get it) -> next problem in bookmarks. This two ways of working with mobile application are very simple and short. Let's imagine we do 10 problem quiz. If we interrupted the quiz a few times, it would be difficult at the end of test to remember first question in detail when analyzing a wrong answer. So, my suggestion to take 1 problem as a basis for GMATClub app.
2) Error logs vs Bookmarks. They both are responsible for the same function: keeping difficult problems to which we could return latter to analyze our mistakes in detail. I'm a strong supporter of bookmarks approach for the following reasons. Sometimes we what to consider deeper problems we've answered right in order to grasp a concept; sometimes we don't want to consider problem we've answered wrong because we've made a silly and obvious mistake. Bookmarks-approach better suit for this function. Moreover, after a week of study we will have a lot of error logs and it will be difficult to manage it. At the same time, error logs help to avoid repetition of problems. It is possible to incorporate such functionality in bookmarks-approach introducing black/white of bad/good bookmarks.
I don't know but maybe it would be useful to have two different applications for math and for verbal.
So, what is my preliminary vision of the first GMATClub app? I think it is math app with 300+ problems divided by difficulty level, timing for a problem, bookmarks, random problem and links to forum threads for each problem. I think we can make such application pretty fast and continue our discussion having something in hands.