One of the various esp8266 boards comes to mind. You can find them for a few bucks off ebay with various levels of functionality. They can act as wifi aps, supp

One of the various esp8266 boards comes to mind. You can find them for a few bucks off ebay with various levels of functionality. They can act as wifi aps, support wpa, and have a few io pins at the very least. Though one of the things you'll discover with a lot of embedded chips is that the integrated editor they are paired with tend to have utilities to help you manage the IO configuration registers, clock dividers, and other less than and/or non-intuitive parts of development.