GoSoapBox is a nice tool for surveying your audience on realtime. I first tried the service a couple of years ago when it was still in beta. GoSoapBox allows you to have your audience respond to questions through their laptops, tablets, and phones.
This morning I saw Doug Johnson use it during his presentation at the TICL conference in Storm Lake, Iowa. Doug used a couple of the handy features in GoSoapBox to get the audience involved in his presentation. The tools that he used were Polls and Discussions. The Polls tool allows you to survey your audience by having them select an answer choice in response to a question. The Discussions tool allows you to have audience members reply to open-ended questions.
GoSoapBox has a handy option called a Confusion Meter. The Confusion Meter allows members of your audience to simply say, "yes, I get it" or "no, I don't get it." The Confusion Meter, like all of the GoSoapBox survey tools, can accept anonymous feedback.
Applications for Education
GoSoapBox allows you to create an event prior to your presentation or lesson. You can select all of the questions and question formats ahead of time. When your presentation or lesson starts, give your students the link to the event and they can access respond to the questions when you prompt them to respond. The Confusion Meter is the simplest tool in the GoSoapBox collection, but might be the most useful for some teachers.