Tired of losing your keycards that somehow slip into every gap available? Most of us won't lose our phones that easily so wouldn't it be nice to be able to unlock your hotel room door with something that stays with you all the time? Say goodbye to your keycard at a participating Starwood property because this is now the new reality!
There's not unexplainable magic behind this - it really is just Bluetooth.
With all that being said, I guess it is still important to provide keycards if they are requested by hotel guests. I cannot imagine having my iPhone in the back pocket of my swimmers should I wish to swim in the pool (or the sea).