A "titanium escape ring"

"It's a simple but elegant-looking ring made of titanium, cut from solid barstock and polished to a mirror finish. But unlike all other rings, this one contains a saw and handcuff shim pick combination tool which is completely hidden from view when worn.

Located on a finger, its always in the exact area needed to quickly access and deploy, even when handcuffed. The shim can be used to open single-locked handcuffs, while the saw can cut zip-ties, disposable handcuffs, duct tape, rope, and other non-metallic materials.

For sale ($80) here, via Boing Boing.