Nest H13000ES Secure Tag.
Just tag in and out on Nest Guard. Put one on your keychain. Give one to people you trust. Set a schedule to let people in at certain times, like your dog walker. It's water resistant and drop-proof. And don't worry if you lose one -- you can easily disable it in the Nest app.
Requires a Nest Secure alarm system starter pack.
By purchasing this product you agree that you are either (i) dealer and contractor who are authorized by Nest to purchase and resell the Product as part of an installed application, or (ii) commercial building owner or developer who hires installing contractors or who has trained, professional maintenance staff to install the Product in the buildings of such owner and developer.