Shaykh Saalih al-Fawzaan was asked:
Using a recorded adhan on the cellphone to notify a person for the time [of prayer], is this [something] agreeable or not?
“If the purpose is to notify him and it does not harm anyone, that is, if some people are reciting Quran in the Masjid and the cellphone calls with the adhan or other than it, then [this] disturbs the people. If it is with him in the house and it is adjusted to [notify him] for the prayer, and it does not harm anyone, then there is no harm” .
Also, Shaykh Abdul-Muhsin al-Abbaad was asked:
Is it allowed to place an Adhan on the cell phone for notification [of the prayer time]?
“There is no harm, that is, so as to determine the time [of the prayer]. For example, before the emergence of fajr the adhan is made 15 minutes before or more than that and a voice is heard when the time comes, then there is no harm [in this]”
[Sharh Saheeh al-Bukhari no. 89 starting at 56:00 until 56:18]
Faisal Ibn Abdul Qaadir Ibn Hassan