Lately, I have been using a free metronome app on the iPhone to help teach gross motor skills. There are several metronome apps so pick the one that works best for you. I downloaded this one since it was free and it works fine for my purposes.
Basically you can set the beat on the metronome to a fast or slow speed. The tick tock on the metronome is an excellent way to teach children stop and go, self control, rhythm and motor timing.
After setting the metronome to a slow speed I instruct the student to only step, jump or hop on the beat. I usually put tape, circles or use a floor ladder to designate where to step or jump. On each tick they are to jump but only on the tick. It forces the child to listen and to stop and go on a beat. Sometimes I will also move the iPhone back and forth as it ticks to provide a visual cue along with the auditory cue. For some children we stay at this level for awhile - practicing different skills (clapping, stepping, jumping, hopping, etc) to the beat encourages motor planning, motor timing, reflexes and self control. When they master moving to the beat, we progress to higher level skills that require similar motor timing - ie jumping jacks, skipping and jumping rope. The kids seem to enjoy the predictable rhythm of the metronome. In my opinion there appears to be immediate carry over of the isolated skill to other functional skills.