Here it is being used in one context at a beatbox battle between then World Beatbox champion Alexinho and the super innovative Soso. https://youtu.be/OjbYK4rujB0?si=SIn-uNHlh2KexsXc
Yabai shout is at 3m23s
It also seems wholly unrelated to anything about this app though, which is a shame, because as someone who knows Japanese, I'm not likely to install something called "yabai" in the same vein that I'm not going to install something called "whoa" or "ohshit". Hopefully that puts me in the minority.