Baby Taser?

Okay, so.
On Friday I had my usual BPP and blood pressure check. My pressure was high (like it always is, HI, that's why I am on bed rest) but Dr F decided he wanted blood work and a NST. I was bummed because I had a crusher of a headache and while I like Arrowhead L & D, I didn't want to spend all day there! Plus, I really get stressed out because I am always afraid I will have to be delivered before B can get there.
However, in this case I got a great L&D nurse, so things were moving right along. The only hold up was that the fetal monitor wasn't picking up the baby consistently and I couldn't leave until he did. The L&D nurse mumbled something about "stimulation" and left the room.
When she came back she had a small item in her hand; it looked like a small flat-headed microphone. She held it against my stomach and I felt a slight vibration. Well, Liam went purely crazy! He jumped like a surprised cat, and started moving like a disco dancer!
Then the L& D nurse sent me home.
Poor Liam. He wiggled and squirmed for hours, and I had contractions for hours.
Now, what I really want to know is, what the H*** is up with the baby taser?