In response to the, "smart lock," aspect of things...
locks, padlocks and handcuffs technological systems can be bypassed if the person attempting to bypass them is given enough time to take a crack at it."
There is a fair amount of liability when it comes to police's usage of handcuffs (which is where most innovation is directed because of money) when it comes to being unable to remove handcuffs. They are intended to be a temporary restraint, and leaving them on for too long can cause damage. Using a cutting wheel or bolt cutters to remove handcuffs introduces even more liability.
Imagine a smart handcuff system that uses Bluetooth to unlock the cuffs. Now imagine a situation like Superstorm Sandy or Hurricane Katrina. There are so many opportunities for water to destroy the handcuffs unlocking mechanism (especially while in the field) and/or for there to be a lack of power for a device that unlocks the handcuffs.
Another situation to consider is technological vulnerabilities. Even the most trusted firewalls or encryption methods get periodic updates because vulnerabilities have been found. Can you imagine trying to make sure that everyone plugged in their smart handcuffs for an update because a vulnerability has (already) been found? More so, if there is a vulnerability with a wireless unlocking system someone could broadcast the unlock codes to all of the handcuffs in a facility. That would be worse than flying over a prison throwing out fist fulls of handcuff keys because of the penetration of radio waves.
Let's not forget about the battery issue. Forgetting to charge your cuffs or change a battery could render them unusable.
I would guess that the potential technology innovations that could be used for, "smart locks," for handcuffs is probably being researched in the, "smart gun," field. The (current) potential failures of one could be easily translated to the other.
These are just my opinions and/or observations. Good luck with your research.