It's called Tapatalk. It's actually for all vbulletin sites. If a site you go to doesn't have it then you can ask them to install it. It's a fast install and it's free for them.
Anyway, the app is $2.99. It works great. Just search "Rap Battles" to find us.
You can go to www.tapatalk.com to check out the features and stuff.
Everybody thank Mic for getting this installed for us.
Enjoy.