Use sticky notes?  Wish they were available for your students to post what they know or ask questions? Collaborate on project, organize their thoughts?

Add a video, and have students comment on the content?

How about a new enter and exit card - use wallwisher.

Brainstorming? 

Here it is - Wall wisher

http://www.wallwisher.com/build

Here are some interesting ideas for using Wallwisher:

Use Wallwisher in the Classroom

1. Students post pictures of different shapes for geometry
2. Brainstorm ideas for projects
3. Post video, have students discuss topic
4. Enter and exit cards.  Students say what they know when they come in, and post what they learned upon leaving.  Students post questions they still have
5. Get feedback from a large audience
6. Post student videos for group or parent views
7. Book Reviews with student input
8.