I just used Wiffiti for the first time as part of a AP US History class discussion for students to post questions or comments that didn't want to interrupt someone else.  First it doesn't work from every phone, only smart phones apparently (my dumb phone couldn't get a message to appear).  Also the messages move around randomly which can be distracting. If I use this again in this way, I won't project for the class to see, just put it on my laptop for me to see during a lecture so that I can address student questions and comments for students who don't want to interrupt or speak up (But  am I enabling their silence?).