https://www.plickers.com/
https://itunes.apple.com/us/app/plickers/id701184049?mt=8
https://play.google.com/store/apps/details?id=com.plickers.client.android
https://itunes.apple.com/us/app/plickers/id701184049?mt=8
https://play.google.com/store/apps/details?id=com.plickers.client.android