Mr Gardner's step dad, Billy Ions, invested in the development of the app after it emerged none of Paul's friends knew how to carry out CPR when he became unconscious.
Mr Ions told ITV News Tyne Tees he hopes the app will help save lives in the future.
The app is designed so that it is easy to use and accessible wherever the person is.
It can be used offline once the app has been downloaded and contains audio videos which illustrate how to carry out various types of life saving tasks.
Kids can learn it. Adults can learn it and it goes right across the board, which is ideally what we wanted, for everybody to be able to download it and learn CPR. It’s a massive thing for Paul’s legacy and his memory, especially for his mam, because it just means something positive can come out of something so tragic.
The launch took place at Paul Gardner's former school in North Shields, Norham High School.
Paul Bull from First Aid North East performed interactive sessions with the pupils to show them exactly how to get somebody into the recover position, administer CPR, and use defibrillators.
He said the app really helps him deliver such sessions.
It’s got videos on there to show you the CPR. It shows you when you need to do CPR and it’s been my pleasure to demonstrate and let the kids have a practice of CPR to give them that knowledge and that awareness that it doesn’t have to be exact. It has to be something rather than nothing.
Sophie Wallis, 15, a pupil from the school took part in the session.
She said "The CPR app is very well executed. It’s easy to navigate and it’s got so much information that if I did see someone in the street that I probably could do something to try and help."
Bradley Bell, 16, said "It’s just a quick click on the app and select which type of first aid and then it talks you through it, tells you how to do it, tells you what to do."
Local cardiologist, Professor Michael Norton, told ITV News "people A) panic, and b) do nothing, apart from hopefully call 999. What we need them to be doing is to be proactive to do something. Anything they do is better than nothing. Number one 999 as quickly as you can. Number two if this person is not breathing and is unconscious we have to presume their heart has stopped. We have to start chest compressions doing CPR."
The problem is most people haven’t done a formal first aid course. If they have then that’s great, but if they haven’t, then having downloaded this app is a really huge step forward in terms of helping people understand what to do in a crisis in this ultimate emergency.