I'd think the penetration of non-cash tipping would be low until some sort of casual payment system got as easy as Bump and cheap enough in requirements (includ

I'd think the penetration of non-cash tipping would be low until some sort of casual payment system got as easy as Bump and cheap enough in requirements (including the phone) that people in those service jobs could use them. Mind, smart-phone capabilities will trickle down to cheap, no-contract phones eventually. Some smart developers and companies will be ready for that.