I received an email from xw25adc, the maker of this nice port expander (so, finally I know how made these I2C Read/WriteNXT-G blocks !). Here’s his description:

In this video you see a NXT brick connected to 4 sensors, one mindstorm.com compass sensor at address 4, one Acceleration Sensor at address 2 and two home brew 8574 input / output sensors at address 40 (on left one) and 46 (to the right). These 8574s are 8 bit input / output integrated circuit chips with a I2C interface. In this project the compass sensor is controlling a arrow at the top of the NXT display, the Acceleration Sensor is controlling a pointing finger at the right of the NXT display and the program is causing four lights connected to the 8574 chip on the right to blink in sequence. The program reads the touch sensors connect to the 8574 on the left and turn on a programmed light when one of the touch sensors is pressed.