Here's an interesting device from Swedish Erotica. It's a black latex ball sheath, connected to a black latex cock ring with three rows of little stimulator nodules. Embedded at the base of the ball sheath is a vibrating bullet for extra stimulation.
The cock ring is designed to be worn at the base of the penis in front of the balls. (Most cock rings are worn behind the balls.)
Intensity is adjustable.
It takes 2 AA Batteries, sold separately.
The packaging says that, when you use this "testicular stimulator with erection support ring," you'll "shoot like you've never done before."