What currently is the single most advanced piece of human technology? - Quora
I would go for this. It is a microcontroller with WiFi integrated and really small, being only 18x18x2.5mm.
It operates with less than 0.3 watt and it is enough capable to stream images, do state of art cryptography, host a web server and communicate with other machines.
It is also very cheap at 3$ in single quantities, but probably it will be even cheaper soon as it will flood in the market.