Not possible with standard Android .

Not possible with standard Android. To sum it up: The alarm on feature phones is triggered by a hardware component (most probably the real time clock, called RTC). Subsequently this component wakes the CPU by raising an interrupt and the CPU runs a dedicated program (interrupt service routine,ISR) which just plays the alarm tune. It's all very low level probably. Android is much more high-level than this and does not support this out of the box (most probably). Any handset manufacturer may of course implement this feature using the same methods as with feature phones, but this is not belonging to the Android OS strictly speaking then. There are too much layers involved to do this without starting up Android. Note: Android allows full device encryption also; how should this work when nothing is accessible without your passphrase? Android couldn't even start.