estratos:
Thanks Lefty,I'm using the old 2KB bootloader, with support for the WDT, since I was unable to make optiboot work on my board.
I'm pretty sure the uno bootloader for the 328p handles WDT correctly. Probably you should try and figure out why you can't burn and run optiboot on your 328p chip rather then trying to add a function to your old bootloader. And again why not just run your calibration function inside the setup function in your sketch?