Marriott has launched mobile check in at 300 locations in North America. You can choose your arrival time, get notified when your room is ready and pick up your room key at the mobile desk at the hotel. You can read more about this initiative on Marriott’s website here.
This functionality is available for those that have Marriott mobile app installed on their Apple or Android device.
Not sure why Marriott is using stock images from temples in South East Asia to promote a product that is available only in their North America market?
I am not convinced that Marriott is going to have a third desk (The Mobile Desk) for people to pick up their keys for check ins done using these apps in addition to the regular and elite check in desks (or maybe they have but is it going to be manned?).
You can also make requests such as wake up calls, towels etc. at four Marriott hotel using the app.
I have seen the self service check in machines at Hilton and Hyatt hotels that rarely work as intended. Getting a proper upgrade even as an elite member sometimes requires smooching with the front desk agent at the time of checking in to find out what is available.
Starwood has an initiative with some Aloft hotels in the North America for a RF coded key that they mail you. Then you can later use the key to access your booked room without ever having to stop at the front desk.
Checking in using the mobile app, having to stop at the (mobile) desk (that may or may not be manned) and having to show your ID etc. is likely not going to be any faster than doing a traditional check in.