Using active tab checking to prevent googling for answers

I was thinking how to prevent users from googling answers of quizzes.
The easiest way I came up was to check weather users tab/browser window is active.
If user goes to other sites or opens some programs I call for quiz submission button.
This just a quick and dirty fix but I would really glad to see this functionality included into quiz module with some additional features. For example a warning dialog in the beginning of the quiz or ability to let users to be away for limited amount of time (5s to disable popup or smth.)
If you think this could be useful please give your opinion even thou you are not capable or just cant spent the time for actual development.