assalamualaikum, the ideas is, it would be nice to be notified a few mins before the actual adhan. this will cause a person to make wudu before the adhan or for someone who may be feeling a bit lazy it will motivate them to at least be preapred insha'Allah. and it would be way more interesting if the notification uses words of affirmation like "prepare yourself for salatul fajr !!" "5 more minutes until salatul duhur" etc.
jazak Allah.

Assalamualaikum.