Response times from conventional emergency services can be too long to prevent irreversible injuries like brain damage, even in the best served cities. The London Ambulance Service manages to attend only 75% of Category A (life threatening) incidents within the target time of 8 minutes.
A consultant neurosurgeon who works with the London Air (helicopter) Ambulance realized that there were many with medical training who could be on the scene faster. He came up with the idea of a phone app that would enable members of the public to contact the emergency services and the nearest volunteer responder. There are two different apps; one for the public, the other for responders. These could be doctors, nurses, trained volunteers with the Red Cross or similar organizations, paramedics or others with a level of first aid training like medical students. The scheme will start in London but there is interest from other cities both in Europe and the USA.
The first phase of GoodSAM started earlier this year with the recruiting of the volunteer Good Samaritans. By July, when the British Medical Association publicized it on their site, the number was just under 1,000. They must adhere to five principles set out in the scheme's brochure (.pdf) Sticking within these rules make it highly unlikely there would be any legal implications although the BMA recommend their members check their insurance.
1. They must ensure their training is up to date
2. They should arrive by foot (in exceptional circumstances of remote locations a car can be used but they must not speed or use official type signals)
3. They must be fully alert and prepared - e.g. they must not have recently drunk alcohol.
4. They must not go outside their skill set.
5. When the official ambulance service personnel arrive, the patient must be handed over to them immediately.
Along with the cry for help alert, responders have maps showing the location of the patient and of the nearest available defibrillators. (These were already being located for the use of trained personnel in a number of locations including train stations in London; the Responder app allows for crowdsourcing of their location if a new one is encountered.). They will also able to directly text the Alerter once they accept the call. If the Responder is not available for one reason or another, they can decline and the system finds the next nearest.
The Alerter's app has now been launched. This can be considered the modern equivalent of shouting for assistance. Once downloaded, it has to be activated using a code sent to their email address. An Alerter's profile can be updated to include their age, allergies, current medications, brief medical history, next of kin details etc in case it it they who has the emergency.
Using the app is not a substitute for phoning the emergency services, but provides an alternative route. In the UK "911" is either 999 or the EU-wide 112 and the app will phone them as part of the process however a Responder could well be on the scene before the emergency has been explained to the operator and an ambulance dispatched. This is best seen in their short video explaining the system:
The scheme has obvious utility in many places and even broader advantages in some. In France for example, their Good Samaritan laws require you to help somebody involved in an accident if you can do so without endangering yourself. GoodSAM (the acronym stands for Smartphone Activated Medics) organization's contact locations are here. You will see they have a "snapshot" map of Responders (I am not sure if this is real time). You might notice there is a cluster just to the right of the center of the map at Mile End Road. That is the location of the Royal London Hospital where the helicopter ambulance service for the city lands. It is, incidentally is where Joseph Merrick, the "Elephant Man", was cared for in the 19th century although the new buildings are much different!