Yes, these devices are to run a node of a chain of your choice; future versions will allow the option to run multiple chains' nodes on one device. With the pairing of the mobile app, the device doubles as a secure hardware wallet that allows sending/receiving of your crypto via your phone.

nimbleNODEs first connect to your phone through bluetooth, then you enable your nimbleNODE to access your wifi through the app. It's recommended to keep your device plugged in 24/7, which consumes a negligible amount of electricity. However, whether it's shut down, unplugged, the wifi resets, or there's a power outage, the device won't require a reindex in order to be up to date, saving the user hours of their time.