Played in a math class today that was using Wacom tablets (writing tablets that plug into a computer by USB) and ClassFlow to pose questions and problems and have students share their thinking and work. ClassFlow is one of my favorite tools for teacher-directed lessons because it easily lets you to stop every few minutes and gather student input by polling (multiple choice), drawing on the screen, or sending text responses. Then you can view students responses, discuss ideas and develop success criteria from what you like, etc. You can also make virtual math manipulatives on it that students move around and send back. ClassFlow works great when you have a device for every student or one per partner, encouraging them to discuss and decide on a response together.