LisaAndRick1,
Sounds like you need the Rental Lock Automater (RLA) from RBoy Apps to remotely manage and automate the guest check in experience, but it does use a hub.
We've been using RBoy Apps for years to manually generate and program codes remotely but the RLA was game changer for us. We just sit back and relax, it downloads the schedules, generates user codes, SMS's the codes to the users (it doesn't email them as yet unfortunately but I can live with that), programs the locks and when it's time to check out it removes the codes from the lock and repeat cycle for next user.
There is a dedicated topic on smartthings that talks about RLA and it's features:
http://community.smartthings.com/t/release-rental-lock-automater-automate-user-codes-with-airbnb-hom...
We've been very pleased with their support and overall experience.
All you need to get going:
1. Yale or Schlage Z-Wave locks (we've used both the Schlage Connect and Yale YRD 240)
Yale: https://www.amazon.com/dp/B00HS1O77G
Schlage: https://www.amazon.com/Schlage-Connect-Touchscreen-Deadbolt-SmartThings/dp/B00AGK9KOG
2. SmartThings hub (www.smartthings.com)
3. Rental Lock Automater (RLA) (www.rboyapps.com)
If you're familiar with SmartThings it's pretty easy but if you aren't familiar with Smartthings then you'll have a learning curve on how to install apps. Rboy apps have detailed step by step instructions on their website on how to install RLA.
Personally I think it's totally worth it because we've also been able to save money by reducing energy wastage using the hub and a z-wave thermostat to turn off the HVAC's after the renters leave and turn it on an hour before they arrive (actually RLA does it for it automatically). It's probably the best $99 we spent on our property 🙂
If you do decide to get RLA, you may also want to check out their low battery notification app which helps us ensure that the lock battery doesn't run out on us.