Amazon Dash Button is very popular so it was hacked.
This button is used for ordering of something product from amazon. If you need e.g. soap powder, you will click on the button and the product will be send to your shopping cart. You approve this order and you will get the product.
Do you want to blink of LED? Do it. You can see tutorial for hack of Amazon Dash button on this website.
It contains STM32F205RG6 (ARM Cortex-M3), WiFi module BCM943362, 16 Mbit SPI FLASH, buttuon and RGB LED.