1. (the good part of condoms) = When encountering a new person the condom serves as an easy way to ask for permission without saying: "Can I have sex with you now". Instead, it's just "Should I get a condom?" Easy enough for her to say yes or no without the pressure.
2 (the bad part) When already familiar with the other person, condoms stop the entire mood and then both people have to wait. IMO, this is the worst part of using them in a relationship.
I think if I were working on a replacement for a condom, I would try to tackle that second issue.