Call Park - Reminder beep

I am looking for a creative solution to add some sort of tone or noise to a BLF field.

I am using Yeahlink T28 phones.

FreePBX (2.9) and Asterisk (1.8.6) are up to date.

I have the call park feature set on the dss keys of my yealink phones. My users push those to park calls. As the calls are parked I have BLF that light to tell the users what call is parked. (they dont work 100% either which is another problem only about 90% - but thats another thread).

In any regard those callers can stay in park for a long time and the users would like a tone or beep to go along with the BLF light to remind them that there is a call on hold.

I don’t know how this could be done… Any thoughts?

Ringback is not an option as they dont want the LINE number to potentially change during the ringback process.

Any thoughts?