[Freeswitch-users] DND emulate key system

Hi, I am wanting to emulate key system behavior of having a BLF key indicate when an extension is on DND. I realize this is not strictly what BLF is. I'm assuming that the DND keys of the phones (yealink) would have to be programmed to send * codes for DND on/off that would call dialplan entries to set presence along with some component to fire the event for the presence message so phones with the BLF keys would all get updated. Before I dig into this under the hood I wanted to ask if others had already done this? Thanks, Kevin