This app was mentioned in 3 comments, with an average of 1.33 upvotes
Prereq for the workshop includes https://play.google.com/store/apps/details?id=com.janyun.jyou which is a poorly rated crapp, it seems.
Alternative app https://play.google.com/store/apps/details?id=com.janyun.jyou
One more app. A little better. https://play.google.com/store/apps/details?id=com.janyun.jyou