Perhaps this idea could be built-in a future cellular phone: To implement a timer for a particular profile or tone.
For example, today I was in a classroom and I selected the the "discreet" profile, but then I forgot to change back again to the standard profile and this afternoon I missed a lot of important calls.
So I think it should be a nice feature for a future phone to select the discreet profile for just 2 hours (the length of the class) and then the phone will change automatically to the standard profile.
Another possibility could be to select the time when the profile will be active or inactive. For example at 8:00PM use the Discreet profile, at 7:00AM use the standard profile, etc.