To add context (and as you probably know). The esp8266 is an older design repurposed as an "IoT" play. It was actually originally designed as a wifi interface.

To add context (and as you probably know). The esp8266 is an older design repurposed as an "IoT" play. It was actually originally designed as a wifi interface. I think it was mostly used in cheap Android tablets. It just so happens that any generic wifi interface IC has pretty much everything required to make a general purpose IoT microcontroller. That is to say, they've all cost an ARM or other cheap core inside as well as the Wifi physical interface. Usually the CPU just does data formatting, interfacing and other management tasks. So, there are lots of those around. In fact if you search for USB wifi dongles on ebay you'll find them for 1 or 2USD. They all have some similar controller inside. The difference with the esp8266 is that they released the documentation, and started marketing the chip as an IoT device. It's neat, because essentially all the of development costs have already been paid off by the Android tablet market.