The tool is free to use, and creating an account only takes a minute. There are several types of poll options, such as open ended, multiple choice, or Yes/No. For a fee, you can get easy to use responses (e.g., text Yes to 22-333) instead of numerical options (e.g., 12653291).
There's a plug-in to PowerPoint that allows you to present right from your slideshow.
I had a lot of fun presenting with this tool. Let me know if you give it a shot!