Widora-AIR V6.0 is an ESP32 (ESP8266 successor with bluetooth) board that is very thin and can be stacked on a breadboard. You can start prototyping you app with bluetooth 4.0 and wifi in a few minutes.
Moreover, you can use atom, arduino and other ide to develop for it in a range of languages (C, C++, LUA, Python, etc.)
This is one of the greatest kits available for the ESP32. Gives you a nice polished enclosure, a back module with connectors and a small battery, an usb type c cable and jumper wires. If you need to have a nice one shot product or a polished prototype using wifi and/or bluetooth, this is the kit you need.
With the protoboards (not included) and upcoming...