They're already used for everything from ordering your groceries to checking your bank balance and booking a table at a restaurant.

So it was only matter of time before a mobile phone app was launched that lets people say yes to sex.

The app is designed to make sure there’s no trouble between partners the morning after the night before, as they film themselves giving consent. But while some health workers have backed so-called ‘sex contracts’, rape victims and student union leaders have condemned them as ‘evil’ and ‘dangerous’.

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'No Doubts': The app uses an Apple iPhone’s video camera to make a 20-second recording of both partners agreeing to sex. The video is then saved in a cloud or server

The WeConsent app is available for £3.20 and is the creation of former Wall Street banker turned philosophy professor Michael Lissick. It uses an Apple iPhone’s video camera to make a 20-second recording of both partners agreeing to sex.

A breathy female British voice asks participants to state their name and to agree to sex. Once the video has been completed the voice says: ‘Consent confirmed. Have fun.’ The video is then saved in a ‘cloud’ or server.

Mr Lissick, 57, said: ‘The videos are twice encrypted and can only be accessed by law enforcement, by a written judge’s order or as part on an ongoing sexual investigation by a college.’

More than 100 people in the UK have already downloaded it.

Sex contracts are being encouraged widely in American colleges. University of Massachusetts student Noah Convicer, 21, has used the WeConsent app several times and said: ‘It’s a great idea. I don’t feel embarrassed asking a girl to consent to sex on video. It protects both of us and it is a mature and responsible thing to do. I use apps for everything else, so why not this?’

Sally Bratton, who sits on the board of the Health Services Association for Californian Community Colleges, which represents two million students on 112 campuses, said: ‘These contracts are a very good idea. They take away any doubt or misunderstanding, which is one of the leading causes of accusations of sexual assault. When you have apps like Tinder making sex purely recreational, why not have an app or contract to protect yourself?’ But Jasmin Enriquez, 23, who was date-raped as a student at Pennsylvania State University, branded sex contracts ‘pure evil’, saying: ‘They are nothing more than stunts and money-generating schemes which distract from the real issue which is education. We need to educate students of both sexes. Informed consent is an ongoing, shifting process which cannot be encapsulated in a contract. A contract fails to safeguard a woman who might change her mind after signing it.’

And Susuana Amoah, women’s officer at the UK’s National Union of Students, said: ‘The idea that consent could be given through an app is a really dangerous notion – this type of technology isn’t the answer to developing better sexual consent behaviour. We shouldn’t be encouraging students to equate consent with “there’s an app for that” – we should be encouraging them to engage in on-going discussions about consent and boundaries.’

Mr Lissick has also launched a ‘What About No’ app, for £3.99. If the user chooses this, a stern voice on the phone says: ‘What part of no do you not understand?’

A video of the person being told no is recorded and stored, and could be used in evidence.

Another version of the sex contract, the Consent Conscious Kit, is being sold online for £2. It includes a paper contract stating ‘Yes! We agree to have sex!’ which couples are asked to sign and date. They can then take a time-stamped photo or video of themselves holding it.