The Sense HAT is an add-on board for Raspberry Pi comprising of a 8×8 RGB LED matrix, a five-button joystick and the following sensors: Gyroscope, Accelerometer, Magnetometer, Temperature, Barometric pressure and Humidity.
The shift register driving the LED Matrix is a LED2472G connected via an Atmel ATTINY88 communicating via i2c at address 0x46 with the Pi. The Multi-Directional SKRHABE010 Switch/Joystick is similarly controlled.
The sensors themselves also operate over the i2c bus:
The IMU (Accelerometer and Magnetometer) through a LSM9DS1 found at i2c address 0x1c(0x1e) and 0x6a(0x6b), with Interrupts on the ATTINY88.
Environmental sensors are represented by a LPS25H Pressure/Temperature sensor at address 0x5c and by a HTS221 Humidity/Temperature sensor at 0x5f on the i2c bus.
In addition, the Atmel chip can be reprogrammed via the SPI interface. The pinout herein only maps the reset and chip select - adding a display or other SPI device alongside the Sense HAT should be possible with a few precautions.