[MrMid]

I was really surprised that modern smartphones are not able to ring an alarm while they are turned off.

My daily driver, Sony Ericsson ELM, rings an alarm each morning I need it, for the last ~9 years. Even when it's off, even if the battery is dead (once had a problem with a charger, couldn't even boot the phone, but it rang each morning for a week).

My iPhone? If it dies, it dies. Not even talking about Android.

[icebraining]

Yeah, old Nokias could do that too. I assume they came with an RTC chip with a programmable alarm, instead of using the main CPU for everything, like most smartphones.

[buckminster]

Old Nokias still do that! I'll be sad when mine dies.

[gpvos]

Yes, that surprised me too. But do you have any idea how your phone's alarm can ring when the battery is dead? Does it have a second battery?

[smichel17]

Most phones turn off before the battery is truly 100% dead.

[cesarb]

IIRC, some of these old phones do have a second "coin cell" battery, which keeps the clock running even when the main battery is removed (the SIM card is usually below the battery, so you have to remove it to exchange the SIM card).

[baroffoos]

My pebble watch does this. When it goes "flat" it reverts to time and alarm only mode which lasts for about 24 hours.

[dzhiurgis]

Interestingly Apple Pay works when iPhone dies