Answer:
Cycle Cycle Cycle.
There is one in every corner and two in every room.
I am million people's wakeup call. What am I?
What calls for help, when written in capital letters, is the same forwards, backwards and upside down?
If you are unsure how to use one then just ask a flight attendant.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.