It's nearly impossible to prove a rape case in court. Because of this, there has been some groundswell of support for relaxing the burden of proof in rape cases to a standard that might ultimately permit some false accusations to result in wrongful convictions (a horrifically bad idea that would likely be a Pandora's box imo).
If you reduce this down to the fundamental tension: either we have to ask women to become dramatically more vigilant and accept some nonzero risk of rape (more or less what we implicitly do already) OR we have to increase the likelihood of wrongful convictions.
As far as I've been able to discern, there is no good solution here. And that's how asinine ideas like this "sex consent app" show up. It's a kind of manifestation of denial.