Hey Olivier,
try this in your makefile for opening a serial terminal from XCode:
serial:
@echo " ---- open serial ---- "
osascript -e 'tell application "Terminal" to do script "screen /dev/tty.usbmodem* 9600"'
killserial:
@echo " ---- close serial ---- "
osascript -e 'tell application "Terminal" to do script "screen -X quit"'
You can then add these rules after and before your upload if you want.