Before online tips were available PAX would always say "Oh, I don't have any cash, but I would tip you on the app if I could". Now they say "Hey . . . I'll tip you later on the app". We all know how that goes. Now, when they say that, I tell them "Oh, thanks, I've put in a request to Uber so that we can thank you through the app to let you know how much we appreciate it". And if they haven't walked away yet, I'll go on and say, "it's not active yet, but it should be soon." First time I tried it, I was shocked that it worked. I can't say it works 100% of the time, but I am surprised when it doesn't. Sometimes the tips are only a $1 but hey, every little bit helps.