The Fuqaha have explicitly prohibited a trader from reciting Durood Shareef, etc. to impress buyers or to promote his stock. Similarly, they have prohibited a guard from reciting aloud tahleel (La-ilaha illAllaah) for waking up those who are sleeping. (Clocks with Athaan, etc. as alarms to wake up people are also prohibited).
[Malfoozaat Hakeemul Ummat]