Handcuffs are one law enforcement tool that has barely changed in the last 100 years, so a company called Scottsdale Inventions figured the restraint device was long overdue for a high-tech makeover. The result is a just-patented design that combines the standard hand restraints with electric shock and chemical deterrents.
The smart handcuffs can be controlled wirelessly much like a stun belt, allowing the officer to trigger a Taser-like shock even if they aren't in contact with the detainee directly. The handcuffs can also be programmed to trigger automatically if certain pre-determined conditions are met, such as walking too far from the controlling officer or coming too close to a restricted area.
If physical restraint and electric shocks still aren't enough, the handcuffs can be equipped to inject a sedative, or even release a knockout gas cloud to stop an escaping detainee.
There's no word on whether these handcuffs will ever enter production, and they do seem like overkill for most prisoners. Perhaps you would need them to move those Hannibal Lecter-types around, but otherwise I think regular handcuffs are just fine.