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I feel very strong doing push-ups in this position and love the challenge of doing them from my feet/toes.

Adding the pulses onto the end of a set gives the abs an extra workout and reinforces proper plank position in the upper body and trunk.  You won't be able to pulse very well if your belly is sagging toward the floor!  Stabilize your upper body by pressing the hands firmly into the ground and try to create length in the torso as you focus on bracing the Abs (similar to the way you do when finding the supine plank position).  Once the upper body and trunk are solid, pulsing with the feet creates a wonderful contraction in the Abs.  

As you are working in these positions, don't forget the most important part... to keep your breath flowing smoothly, in and out.