TisaneAPI - Detect hate speech, cyberbullying, and more in 27 languages
CONV. - Convert YouTube video to MP3, GIF or MP4
YouTube Kids - YouTube for the youngins on iOS and Android
Downie - Video download for OS X. Downie supports at this moment over 1,000 different sites.
Kidy - Intelligent, safe search for kids
Yout - YouTube to Mp3 Converter