What is the ruling on praying for the Prophet (peace be upon him) using a loudspeaker after the Adhan?

Prayer and peace be upon the Prophet, may Allah bless him and grant him peace, after the Adhan is legally required for everyone who hears the call, as the Prophet, may Allah bless him and grant him peace, said: "When you hear the Mu'adhdhin, say what he says, then send prayers upon me..." However, vocalizing this through loudspeakers in the manner that Mu'adhdhins have customarily done in some countries, which has become a religious شعار (emblem/slogan) in excess of the prescribed Adhan, is a blameworthy innovation (bid'ah). Scholars have issued fatwas that the original act is a Sunnah, but the manner of doing it is an innovation.