Maybe this could be a solution to the CPS problem that we are having - especially since every student will have an iPad.  I have not looked into the data that is produced, but it might be something someone might be interested in researching!

I think all these online response systems requiring the use of the students' devices are wonderful. However, is there an impact, perhaps one that might be significant enough, of the use of students' devices in that the device is personal. Do students using an older device relatively to others in the class be sensitive in its use When majority of the classmates have the latest ohone device models. Also when teachers and faculty be comfortable of students while using the devices in the exercise are distracted (actual or presumed or perceived) with other apps during that exercise? 

Also when the wireless access point be robust and reliable enough when it experiences a surge/flood of signals when large numbers of simultaneous responses are transmitted in a small time window. 

My observation is that teachers do not want to be encumbered with such distractions, uncertainty and confrontation when only partial student responses are recorded due to technical issues. The latter also leads to the technical support of student devices which is unknown (which version of OS), unfamiliar (what other apps or potential of interdependencies) and uncertainty (are you sure they are not checking on their apps while others are still thinking of their responses?)

Will cost you to get benefit of asking multiple questions, securing data & privacy, and being able to export data. $75/year for basic protections & additional questions, or $180 to add colleagues and get all Mentimeter has to offer. Device agnostic - works across platforms. Real time answers to multiple choice, open-ended or scaled responses.