A phone-activated cock ring

She pulls out a purple cock ring, and holds it in the air admiring it.
"This will make our sex much better, for both of us! And the best part is, it can be activated from an app on my phone, so when I'm horny in class... you'll know it ;)"

Let's give it a whirl. She untucks you from the blanket, pulls off your restraints, yanks down your boxers, and fits the cock ring snugly around you. She hits a few buttons on her phone and you start to feel a faint vibration along your shaft.

She taps a few more buttons and the pulsing increases. Your penis quickly grows to a full-on erection.

"Glad to see it's working," She grins.

She reaches into her drawer and pulls out a vibrator of her own and starts getting herself riled up. She then, shifts and mounts you reverse cowgirl style. Her large ass pounding down onto you, as she moans.

"This cockring is the besssttt."

Before long, she is cumming again, this time in synch with you.

"Oo, I can tell we're getting some chemistry." She smiles and cleans you up.

"Was that good for you?" You tell her Yes.

"Tell you what? Tomorrow, I'm going to give you a little more freedom."

With that, you both quickly doze off, she undoes both your feet and lays on top of you, intertwining her legs with yours.