For the last decade or so hotels have faced the challenges from online travel booking sites such as Expedia and Booking.com as they seek more power over selling their rooms.

But the mobile revolution creates a new threat: These booking sites usurping the hotels’ power in their own lobby services and over in-destination activities.

That’s the view of Tom White of Macquarie Equities Research, who argues in a client note that the mobile reach of online travel sites such as TripAdvisor, Expedia, and Priceline could “more deeply penetrate the day-to-day operations of hoteliers.”

“For example, could the average leisure traveler one day check into a hotel via their TripAdvisor/Booking.com/Expedia app (bypassing the typical ‘front desk’ check-in experience entirely), or perhaps upgrade to a nicer room or order room service breakfast for the next day — all via a mobile app on their way up the elevator to their room, with the online travel company and the hotel splitting any incremental economics or ARPU (average revenue per user)?” White asks.

White says he wouldn’t be surprised to see new merger and acquisition activity as the booking companies go after mobile check-in products such as Room 77’s Checkmate service.

Online travel company expansion beyond travel search and booking is being driven by mobile trends and will extend into in-destination services such as dining reservations and tours and activities, White argues.

White points to TripAdvisor as having a headstart over its rivals in getting a handle on in-destination activities.

When I interviewed TripAdvisor CEO Steve Kaufer in October, he offered a vision of how TripAdvisor wants to own the entire travel cycle, including becoming a sort of in-destination concierge.

White points out that TripAdvisor has 108 million monthly mobile uniques, reviews of 2 million restaurants and 400,000 attractions, as well as offering mobile city guides for 80 markets that work online and offline.

In addition to the online travel agency competition/collaboration with hotels at the destination, they will likely battle against one another for supremacy, as well.

Expedia.com already reserves plenty of homepage real estate for tours and activities in its latest redesign.

And, White notes that Brett Keller, Priceline’s chief marketing officer, recently expressed the hope that the company will “expand into enabling hotel check-ins and on-site purchases” through mobile features.

As White states, it is going to take a while for the battle to take further shape, but the focus of the next heated contest pitting OTAs against hotels on the one hand, and OTAs against other OTAs on the other, is expanding beyond search and room reservations and into the hotel lobby and the tour around the corner.

Photo Credit: In the not-too-distant future, hotel guests may increasingly skip the front desk for check-ins and use a hotel or online travel agency mobile app. The Novotel Poznan Centrum lobby in Malta. Boudewijn Berends / Flickr