Of course an app is quicker but there may be ways of manipulating an app.
I say there should be 1000s of
Sex JPs available (probably most late at night after the pubs shut) who should be on call to sign and witness a paper record formally, that congress will shortly take place.
You can take your chances but I would advise it: he (or she) should hang around for the next 10 minutes or even up to an hour to acknowledge certain actions during congress be mutually agreed..
ie the couple may decide to try something new, say toe-sucking (as popularized by Sarah,
Duchess of York).
Cost? maybe on the ailing NHS (there may be delays so couple (or group) may have to wait a few days) with an option for private JP. May even be Sex JPs who will do it for free

?
Top cop's bizarre push for a 'consent app' - forcing lovers to fill out a form on their phone every time they want to get intimate
NSW Police commissioner has proposed the introduction of a sex consent app
www.dailymail.co.uk/news/article-9371829...-app-introduced.html