Hmmmm...cell phone? Set to vibrate!
I've seen some remote controlled devices somewhere. I recall that one was a butt plug and the other was a clit massager. I could imagine having a woman wearing a clit massager while walking about town. Perhaps sit her down for a nice lunch/dinner at a well-lnown restaurant. Sipping wine while holding down the button and watching her lower lip begin to quiver and her body dtart to move about....woof!