We now have Durability Alerts ! 

Commands

/durabilityalert (/da) - the base command

/durabilityalert toggle - toggles the alert per player (set by user)

/durabilityalert armour <number> - sets the percent at which the armour durability warning will start to show (set by user)

/durabilityalert tools <number> - sets the percent at which the tools durability warning will show (set by user)

/durabilityalert type [percent/durability] - sets the warning values to depend on either percent left, or durability left (set by user)

/durabilityalert enchant - Toggle whether or not alerts hould only be shown for enchanted items

/durabilityalert status - Shows the current settings for the user (edited)