Yes easy enough. Unless they had their bottom rib removed to get that hourglass figure it's not exactly hard to
guestimate where ones lower rib is from the armpit down for example. And in 99% of matches there is no camera evidence so a line across the net won't help in terms of "evidence" ...
As in the FIFA debate it should be applicable and executable on most if not all levels of play. If there are no camera's who can check afterwards what a service judge's performance was or immediately after a disputable call. No feedback, no behavorial adjustment?
(probably left some loose ends here and there since I'm rushing in these posts in between

)