Re: bias
A more workable solution would be for people to spend more time socialising face to face and
not through Twitter/Tinder etc, thus learning how to read cues in others. This app doesn't solve anything because a girl can change her mind at any point (including after the form is signed) and that should be respected.
So, as a start, beer duty should be reduced to encourage mixed socialising in pubs.
If you really want a technological 'solution' then maybe some kind of encrypted and escrowed audio recording of the whole night, which can only be accessed in the case of a dispute. (I'm just thinking out loud here)