When presenting in Keynote from your iPad, instead of carrying around a laser pointer, use your finger.

The laser pointer tool in Keynote lets you accentuate your point with the effect of a laser light pointer, with a comet like trail.

To activate the pointer, touch and hold anywhere on your iPad screen.  A red-and-white point appears beneath your finger.  While holding your finger down, trace your finger to the point(s) you want to emphasize and the laser pointer follows.  Lift your finger to turn off the pointer and resume.