I2C is used at run time in 12 crates (of which 9 optionally). It is a direct run-time dependency in 5 crates.

Depender (with downloads and own rev deps) I2C version
3.5K 4 i2c-linux optional ^0.1.0
950 1 ddc-i2c ^0.1
120 i2c-tiny-usb ^0.1.0
550 2 nvapi optional ^0.1.0
i2c-i2cdev ^0.1.0