Audiance Response Application

I want to make a simple audience response application. When I deliver talks, I want to engage the audience. Suppose there is an audience of 100 people, and I am giving a talk. I want to have the ability to flash a question with max. 4 options for answers on the screen (using Powerpoint). I want the mobile application (for the audience), so that the audience can select one of the answers from the options I flashed - they will get 30 seconds to answer / or some system to monitor the time allocated for them to answer & some sort of confirmation on their screen that their response has been taken. I answer from each mobile phone only. After the allocated time, the application should be able to process the answers from the audience and collate it - and show a consolidated graph (optional - pie chart or bar chart) .. I should have the option to pre-select the type of graph that I want to display - pie chart or bar chart - the application will immediately process and show the break-up (% and Number) of the response received. If this can be integrated to powerpoint, that will be the best.