Yes! Here's how it works:
You can choose to call anyone from your Contacts. When the person you're trying to call doesn't have an ONSCREEN device, they will receive a text message with a link to download the app from their app store.
Once the new user downloads the app on their phone, they simply need to open the app, it will automatically join your call.
They will need to accept Camera and Microphone permissions to participant in the video call. Now, you will see them on your TV, while they see you on their mobile device.
Standard data rates may apply if using cellular service.
Here is a quick video on how ONSCREEN calls work: