My first reaction is that I have been waiting for a front runner in the mobile key space. I use mobile boarding passes for my flights, and complained when an airport didn't support it. It seemed natural for me to want them for my hotel room key.
Of course this is tempered quickly by a recent experience where the mobile ticket scanner at the TSA check was not working. It cost me several minutes while they scrambled to figure out an alternative to me having to go back to ticketing to get a physical copy. On my way out, the TSA agent said I should always have a physical copy just in case. But if I subscribe to that, then why bother with the digital copy at all.
What are your thoughts? How would you support this in your property?