By adding a camera module to your Raspberry Pi, you essentially get a portable, lightweight, and easy-to-hold-or-mount internet-connected camera.
Command
raspivid -o - -t 0 -w 1920 -h 1080 -fps 40 -b 8000000 -g 40 | ffmpeg -re -ar 44100 -ac 2 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero -f h264 -i pipe:0 -c:v copy -c:a aac -ab 128k -g 40 -strict experimental -f flv -r 30 rtmp://a.rtmp.youtube.com/live2/[your-secret-key-here]