This is a huge issue for me.
I found this to be an awesome feature with the Blackberries I had been using over the past 5 years.
Phones with terrible battery life , like the Galaxy S3 and the now NExus4 which i have just bought (which is one amazing phone btw) should all come standard with this feature.
Countless times i have been places over night and forgot a charger and want to conserve battery for the next day, but still need to set an alarm to wake me up. And the blackberry saved my life every time with that simple feature.
Quite shocked that the new nexus device doesn't have this feature. Still love the phone, but I just don't understand why this isn't done with android devices, yet blackberry does.