There are a couple of tools that are phone-based methods of engaging the audience to give them their say. One is Zuku which is a text message audience polling product. A speaker or meeting planner can set up an account for about $300 per year for unlimited use. For this, they will receive a phone-based audience polling and question system and a private webpage to set up and retrieve the responses. When a speaker or meeting host wants to receive questions or conduct a poll, all he or she has to do is ask the audience members to pull out their phones, and send a text message to a unique 6-digit short code. This message can either be a text question, or a numerical response to a multiple choice question. Responses are immediately tallied and displayed on a password protected page on the ZukuWeb website. This page can be protected to the audience on a screen for everyone to see just like a traditional audience polling systems, or reviewed by the speaker or moderator to respond to questions.
Another tool is VisionTree provides full audience polling, text questions, conference messaging, conference agenda services and more using the iPhone and other web-phone products. THey will come to your meeting, set up a local wireless network, and will pass out iPhones to those attendees who are not already carrying them. Questions can easily be submitted anonymously to the speaker.