Here is the sensors.yaml entries I mentioned in the video. Just replace the YouTube ID and the YouTube API and you are good to go.
- platform: rest
resource: https://youtube.googleapis.com/youtube/v3/channels?part=statistics&id=[[YOUTUBEID]]&key=[[APIKEY]]
method: GET
value_template: '{{ (value_json["items"][0].statistics.viewCount | int) }}'
name: "YouTube Views"
scan_interval: 900
- platform: rest
resource: https://youtube.googleapis.com/youtube/v3/channels?part=statistics&id=[[YOUTUBEID]]&key=[[APIKEY]]
name: "TSH YouTube Subscribers"
value_template: '{{ (value_json["items"][0].statistics.subscriberCount | int) }}'
scan_interval: 900