When i was in labor, there was someing inserted that could detect a contraction before I felt it. I'm not sure what the purpose was, but my partner would watch the monitor, and when it would start to show activity, he would warn me it was coming and to get ready.
It seems this could be really handy in T&D. Insert the detector, then tease all you want with fingers, mouth, vibrator, etc - until the detector sensed an impending contraction - then stop the stimulation.
Seems this could be done endlessly and mercilessly. :-)