Some i2c devices function by reading and writing to registers, here is an example: http://www.seeedstudio.com/wiki/Grove_-_I2C_ADC

There is already a TODO inside the DeviceRead method but I think it's worth tracking as an issue since it will be needed to implement drivers and the API needs to be different (we'd need to pass the registry id). Suggestion API:

func (d *Device) ReadFromReg(reg byte, buf []byte) error{}
func (d *Device) WriteToReg(reg byte, buf []byte) error{}