Duo has a feature called Knock Knock that turns on the caller’s camera as a preview of who’s calling.
It also gave some relationship/sex advice that was ok but to me it seemed like common since some of it said don't talk to your partner about what you would like during sex or when your about to go to bed so your partner would be more open mined.
Secondly, all it really has was pick up lines while some were ok must sucked or were fairly old.
One said do you like math if so I can add you to the bed subtract your clothes divide your legs and then multiply. Assuming the app did work with phones you would probably need the person phone number already which you wouldn't really need a pick up line for just call the person and ask if he or she wants to go to the movies or get something to eat.
You can start a video call from a message in i Message, or you could even add a contact as a favorite in the phone app to quickly start a Face Time call.
In i OS 10 you can add those favorites as a widget and start a Face Time call from your lock screen.