Sync or link softphone to desk phone Merged

Primarily in our office, all users are on desk phones. However a few employees are in and out of the office enough, that they have both a desk phone and a softphone (via the app on their smart phone). That way they can answer on either device, the desk phone when they are in the office and the app when they are out of the office.

While this is very convenient it does lead to some frustrations and usability issues. If a call is picked up on the softphone, it shows up as a missed call on the desk phone and visa versa. Also, if an employee is on a call on the softphone, the desk phone doesn't show up as busy and calls still come through on it.

There should be a way to link or sync the softphone to the desk phone. Ideally, we want a call to only show up as missed if the employee doesn't pick it up on either device. Also, if an employee is on a call on either device they should be considered busy on all devices.