1. Paint guns that ‘mark’ the criminals.
2. Snap a bracelet or ankle restraint that tracks them even if they escape instead of handcuffing
3. Some kind of frisbee like or boomerang like device that can latch on to criminals instead of handcuffs.
4. Handcuffing with a diff design of cuffs rather than one that stresses the body.
5. Robots that can be sent forth instead of cops armed with guns and tasers.
6. Blob like net material that captures criminals
7. A removable/dissolvable chip for various crimes from felony to DUI to burglary. No arrests.
8. Built in breathalyzer in automobiles/vehicles.
Number 4 would be difficult to achieve because if the body is not stressed then it likely doesn't function as an adequate restraint or it wouldn't be one that could be put on someone uncooperative. Even cuffs today are not always sufficient restraint.
Number 7, these exist today. There must be an arrest and a conviction in court because police judges do not exist yet and so people are innocent until proven guilty.
Number 8 exists today and can be court ordered.
The remaining entries would be less that lethal and not non lethal. There's a very big distinction. Bean bag guns are non lethal when used optimally but circumstances of a police action dictate that optimal conditions do not exist in the real world.
The problem with policing isn't the physical tools that they have it's the mental tools they have. They have a difficult job in difficult circumstances under constant "arm chair quarterbacking". That does not excuse bad behavior in any way but we as a society have construed a set of polices to guide officers in what they are allowed to do and what they are not. These policies give officers the benefit of the doubt that their actions are always correct and justified for the circumstances. There's also the police culture of protecting each other instead of doing what's right.
What needs to change is the polices that govern an officers acceptable actions. This is achieved through of the local city governments who appoint the chief of police and enact the polices that are followed. The sheriff is an elected office as well. These are local community changes that can be made quite quickly if the community desires. Policies need to no longer assume that the officer is always taking a justified action. De-escalation and non arrest, if warranted, should be a primary focus instead of the current bully tactics.
Additionally the culture of the police officers must change. Individually they should evaluate if their actions are correct and the actions they see other officers perform. The blue gang mindset needs to disappear. If officers behavior in both their personal and professional life was conducted in an irreproachable manor much of the us vs them attitude would vanish.