Tomu [Discontinued] _ARD_SHIELD_GPSGSM Pimoroni have taken the ESP8266

Pimoroni have taken the ESP8266 (ESP-12F) module and added the necessary circuitry to allow it to interface cleanly with the Raspberry Pi via serial communication

compress the spring

512KB flash and 64KB SRAM

and an ATMega328

it can get old quick

Tomu [Discontinued] _ARD_SHIELD_GPSGSM Pimoroni have taken the ESP8266Only 13mm long, Tomu really puts the micro in microprocessor. It's fully open source development board with the silabs Gecko EFM32HG309 processor, on a little board that can slot right into your computer or laptop USB A port (USB C users will need an adapter). The board feature two tiny LEDs, and two capacitive touch pads, as well as a native USB bootloader. While it was originally designed for 2 factor authentication, it's great for very tiny USB