ShowPointer is a fine alternative to the traditional laserpointer if the event features several presentation screens running in parallel. With ShowPointer the speaker can easily highlight areas at slides in a way that can be watched on all screens.
ShowPointer is operated from a touch screen displaying the signal from the PowerPoint presentation. Touching the screen will show a standard laserpointer dot on top of the presentation but as an extra advantage movement are tracked and will stay on screen for a short while if the presenter wants to circle a section on the slide thus carrying the interaction to all displays at the conference.
There is more info at the Touchpointer site which features the commercial version of the product.