Interface Arduino with GPS, accelerometer, gyro, magnetometer, barometer

Other Hardware Sensors
7

The 3.3V is an output.

If you use pull-ups on the I2C bus to the 3.3V (NOT the 5V), it is a little compatible with 3.3V.
I'm writing a playground article about level shifting right now: Arduino Playground - I2CBi-directionalLevelShifter