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