While HomePass™ allows you to securely share access to any device in your home, selectively to any guest, there are a few caveats with technologies that work beyond Wi-Fi.
Visible Multicast and Wi-FI Direct devices
Users provide with Guest or Internet Only access, will still be able to see broadcast and multicast traffic from other devices connected to the same Pod. This means that your guests may see Home devices (typically through AirPlay or mDNS/ChromeCast), though they will be unable to communicate directly with them.
Cloud managed devices
Devices that are cloud-controlled (such as Nest Cams and Ring Doorbells) will continue to be accessible by their respective smartphone apps and credentials, even if the Guest Access zone does not permit direct LAN communication to the devices.