I considered a WiFi enabled lock - in the end I opted for the low tech master lock key safe - I'd space to mount this at the front door - works really well for me.
Hive or Nest work really well in conjunction with smart meters (fitted at zero cost by my energy supplier) in between guests I can remotely manage the temperature of the house to help control costs.
I'm sure that with the addition of open API by Airbnb there will be lots of startups offering new products and services to hosts for further automation.
Happy hosting!
Graeme