Plickers - paper based "clickers"

I love the idea of student response systems such as Socrative, but my students don't have individual devices to use.  I came across Plickers and tried it out right away.  To use Plickers in your classroom you only need one device (apple or android).  Students each get a card (that you can print) that looks like a QR code.  Depending on the orientation that students hold the card they are presenting a different answer.  All it takes is a quick pan across the room with your device and you'll get all of the students responses.

I will admit the the setup is a little cumbersome if you want to track individual students.  It's not as easy as some of the other apps, but it's great low tech option.  A couple of notes to help you use them in the classroom.  Make sure that when the students hold up their cards their fingers aren't covering any of the code.  Also, resist the urge to laminate the cards.  Yes they will last longer, but the glare will prevent the camera from properly picking up the image.

What quick assessment techniques do you use in your classroom?