No. The Fingbox can only monitor a single network, hence it cannot monitor guest networks or any multiples of networks.
Guest Network is separate from the main network and creates a separate network gateway so none of the devices from the guest network can access the main network. Fingbox can only manage one network gateway on which it is activated on.
The Fingbox is designed for the average home network. It can manage/control one LAN or VLAN and one 2.4 GHz /5 GHz Wi-Fi network with the same SSID. You will need to pick one of your SSID to monitor/control via the Fingbox. You will have to choose the network you want to monitor/control to put the Fingbox and use the Fing App to access the Fingbox.
There a few things that are best practices:
1. On a large number of routers the Admin user ID an password are right on the bottom of the router.
2. Some Guest & primary networks share the same password.
Every home grade router has these features and please follow these steps for adding security:
1. Change the admin password to something with 11 characters or more. 11 characters as a base make it hard for password crack utilities to break. Having more than 16 is even better.
2. Change the Guest network password or even turn it off when not in use.
If you want to monitor the Guest network, you could use a separate Fingbox and just block all their devices.