self programming arduino atmega168 over I2C

Dear all, I have 3 stack modules conected with each other over I2C. On each stack module there is atmega168. i would be happy if somebody can guide me in programming a boodloader for atmega168, which can let the controller to be programmed over I2C. I know, that i should write a bootloader which give me the possibility to programm the atmega over I2C. But How? is there any examples or tutorials? Thank you in advanced

I don't think any one has done that, do post the results if you succeed. The device will need to be in the I2C slave mode.