If WebCore allows you to subscribe to user created events, my gut says it does not, its quite simple.
Subscribe to location event shmdelaytalk (event created by SHM Delay)
Then check for the following in the event value field
entryDelay - event data has the delay in seconds
exitDelay (keypad created exit delay - system is not armed) - event data has the delay in seconds
exitDelayNkypd (non keypad created exit delay - system is armed) - event data has the delay in seconds
and if one of above values is true, set buzzer on for delay seconds
You may want to subscribe to the alarm status change to catch an arming cancel, and a disarm at entry
When it changes to disarmed/off, set buzzer off
----or—
If you have a keypad you can monitor the device attribute “armMode” for:
disarmed, armedAway, armedStay, armedNight, entryDelay, exitDelay
If none of the above work for you, modify module SHM Delay Talker to a stand alone smart app controlling the buzzer.