Thanks to mikeprimm for adding a couple of requested features to DynMap which made this feature possible.
New commands:
/wb dynmap <on/off> - turn DynMap border display on or off.
/wb dynmapmsg <text> - DynMap border labels will show this.
New permissions:
worldborder.dynmap (Op): Can enable/disable DynMap border display integration
worldborder.dynmapmsg (Op): Can set the label text for borders shown in DynMap
Also, a slight improvement to how boolean values are determined from command input; it accepts "y", "yes", "true" instead of just "on".