Looks like they use Phone number with SMS verification for account creation.

Wumbo

BlokchainB

I will install in IPhone as it is not compatible with my android. 

mdominicorobin24

bitcoin_beginners

Introduced here  https://stacker.news/items/650031, it's available for both Android  and iOS users.

Android: 
https://play.google.com/store/apps/details?id=com.jippiApp.jippi.prod

iOS: https://apps.apple.com/us/app/jippi/id647138013