After pairing my Neurosky Mindwave mobile headset to my IPhone, I recorded multiple sessions, and emailed them to myself. However, when I opened the data in excel, absolutely no information at all had been recorded. After re-pairing my phone and restarting the app (and after sending the files to myself) the app had still recorded no data! I was extremely disappointed.
That said, the problem seems to be caused by looking at and/or sending stored data. Once that is access, the app fails to record data. The only way I've found to "fix" it is by forgetting the Mindwave and then re-pairing it with my iPhone (which is tedious but gets the job done).
Overall, I don't know how accurately the app measures the EEG recordings, but anecdotally, in my own case, it seems to correlate with particular mental states.
Lastly, it would be nice if instead of recording every second of elapsed time on the EEG excel file, it if instead recorded the exact time of day to the second.