alert notification as master or periferal?

Question

I'm currently working on alert notification service. Correct me in case I misunderstand it. 
 having nrf51822 as peripheral with AlertNotificationServie will impose to have the app (ios at the moment) always running. 
 In case nrf51822 is a master there is no problem with app to sit memory. for this I'll have to use S120. 
 Is the master the right way to do it? 
 Anyone having same thoughts? 
 Thank you

Ole Morten · Accepted Answer

An iOS app can keep a connection to a Peripheral in the background, so there shouldn't be any reason to not have the iOS device as the Central. 
 However, with the Alert Notification Service, it's most often the device that has the notifications (i.e. the phone) that would be the GATT Server, and the device accessing them (the device) would be the GATT Client. As explained here , this is however independent of the GAP role.