Theoretically, in an ideal world with sufficient software quality, yes.
https://www.google.com/search?q=android+alarm+problem
https://www.google.com/search?q=iphone+alarm+problem
But then the hardware might stop working suddenly, this possibility still remains.
Strongly seconded.
And ideally place the additional alarm device out of your reach so you have to get up first to turn it off 
.