NEW YORK ( MainStreet) — The Hotel Tonight promise to travelers is simple, and it is compelling. Book a same night hotel room using the app (on iPhone and Android) and the savings can be up to 70%, said Jared Simon, COO of Hotel Tonight.

True? False?

Or more pointedly: are the Hotel Tonight savings better than those found on competitors?

For starters, know the market for same day hotel booking is huge - around 15% of all rooms sold, estimated Simon. He also pointed to accepted hotel industry wisdom that on any given night, 40% of rooms go unoccupied, and for the hotelier, that is a monumental loss.

So the Hotel Tonight promise to hoteliers - it says it works with 10,000 of them - is that by offering a healthy discount, they may attract a guest who will fill a room that otherwise produced no revenue at all. And a hotel guest, even one staying at a deeply discounted rate, may generate yet other revenues - perhaps $10 for WiFi, $20 for a martini at the bar, maybe $5 for a small water from the minibar. It all adds up to found profits for a hotel operator, thus the fast acceptance of Hotel Tonight in the usually sluggish hotel marketplace.

Not even three year's in the market, HotelTonight is helping to fuel a revolution in booking hotel rooms where, suddenly, same-day booking looms as sensible and wallet friendly. A key to the app - because it was built for mobile - is that it presents a curated list of rooms that has been pared down to a handful of properties in most towns. Yes, that cuts down on choice but it also is a mobile friendly presentation.

The company also focuses on hotels that will appeal to a mobile first customer, that is, hip boutique hotels and also cool luxury such as Kimpton and Loews.

Click around and there are options for booking two through five night stays, as well as the bread and butter one night.

Bookings open at 9 a.m. local time for the hotel and, occasionally, the allotted inventory sells out.

How good is Hotel Tonight? Travel blogger Rebecca Garland, who posts at MsAdventuress, offers her loud praises for Hotel Tonight.

"Over the New Year's holiday I traveled to Chicago," she said. "During that time I rented out my Seattle townhouse through AirBnB. The AirBnB renters needed to stay in my townhouse one extra day after I returned from Chicago, which meant I had to find a place in Seattle to stay for one night. The afternoon I was flying from Chicago to Seattle, I sat in O'Hare and logged on to the Hotel Tonight app on my iPhone. I discovered that the Hotel Monaco, a Kimpton hotel, in downtown Seattle was available that evening for $110. I then logged out of HotelTonight and scrolled through my usual booking sites - Kayak, Expedia, Travelocity, Kimpton's website. None of these other websites could come close to Hotel Tonight's offer. The lowest price I could find was over $150." So she booked via Hotel Tonight, and you can count her a happy customer.