Gauntlets used by the Black Widow . S.H.I.E.L.D. implanted the gauntlets with special technology that enabled them to be used for decades. They primarily shoot a cable for swinging and fire the "Widow's Bite".
Widow's Line - Retractable grappling hook and cable connected to the gauntlets, mostly used for rooftop gliding, rappelling and climbing up steep cliffs and hills.
Widow's Kiss- A high frequency electrostatic charge that also act as percussive energy blasts, that it effects can be felt for at least a month. It can deliver charges up to 30,000 volts. The "Bite" can be set to deliver minor shocks that causes stunning or high voltage currents that can be lethal.
Radio Transmitter - This enable Widow to lock on to a target and track its every move. If placed on a moving vehicle like a car or bike, it enables Widow to track down their location.
Marvel Database Black Widow's Gauntlets Article- http://marvel.wikia.com/Black_Widow's_Gauntlets