There are two societies. One highly advanced with AI, posthumans, post-scarcity economy and off-Earth resources. So gold and platinum is what a Mercury base resident just calls “rocks”. They have emerging nanotechnology of the full-blown utility goo variety developed a few years in, analogous to what Apple ][ and CPM machines were to the information age: amazing revolutions but just getting started in terms of features and power. They also have superconductors, and ordinary electronics/photonics/spintronics far in advance of what we have today in 2016.

The other society is the level of tech we have today but on hard times socioeconomically so they don’t get the full benefit. Think of slums and urban gangs in control with a strong government absent, busy with larger problems in a “mild” apocalyptic decline.

Now the advanced society decides to send a mission to this particular city, to help them recover. They can *afford* to take care of everything, make great new buildings appear as if my magic in a span of days, feed everyone, educate anyone who will listen.

But the big problem is the people's current social structure, dominated by gangs and lawlessness. Replace the slum with a shiny new city and the anti-social people will misbehave and tear it down again and oppress each other.

So, a more subtle approach is needed. As an introduction, the missionaries are giving everybody a gold coin. There is a pile in the community center and you can go handle them and appreciate the pile, but can only *take* exactly one. That’s easy, with security measures in the building around where the pile is stored.

But afterwards, the coins **cannot be stolen**. Each is registered to an owner and the missionaries will take action if one is taken from someone else. Now certainly people carrying around these coins will be carrying around in fact powerful surveillance devices everywhere they go and gather!

A missionary staffed police force can know who took the coin from whom and show up to deal with it.

But, I want something more astonishing: the coins, worn as talisman, can protect the owner against violence from the gangs. Not just an automatic 911 when he’s in trouble, but seem to “protect” him in ways that seem like magic to those involved in the altercation.

With the technology as noted, what can the coins **do** to the owner and any threats from other people?