It uses NXP LPC8N04, and features nine 0.4 mm slim orange LEDs for the light show and feedback. The MCU itself consumes only 900uA at 8MHz and 200uA at 1MHz. Given that NFC readers provide power continuously, there are many application that could be implemented on the business card. I haven't came up with anything fancy yet, except for hooking up I2C sensors, and using LEDs and time interval that card is held against the NFC reader to change the mode of operation. If you have any ideas, leave the comment below!