"The benefit to the digital check-in is that your phone is the key," said Kimberly Elder, director of sales for the Harpeth Hotel, adding that many guests still prefer the plastic key cards.

Eli Fuchs, regional director of operations at Valor Hospitality Partners, which has Hilton and Holiday Inn Express hotels in its portfolio, says digital is the next wave in hotel room door technology.

"Traditional hotel room keys are staring down the end of their existence," Fuchs says.