Emergency services can instantly assess patients from afar using live video streaming technology.
A new feature on the GoodSAM platform enables medics to initiate a video link with 999 callers, allowing them to determine the severity of casualties before arriving on scene.
Two air ambulance services have begun using the technology, which aims to improve how emergency resources are deployed.
Another feature, still in the trial stages, will allow crews to measure a patient's pulse using just a video stream, the developers said.
The "instant on scene" technology works by sending a text message to the 999 caller's phone.
By opening a link, the caller sends their location, grants access to their phone's camera and the video streaming begins.
The 999 call can continue while the video is streaming, allowing emergency services to provide advice and assess the patient.
The technology, which works on any smartphone, does not store the video to the device and does not require an app.
Kent, Surrey and Sussex Air Ambulance and Great North Air Ambulance have already begun using the technology, while GoodSAM is in talks with to introduce it with other services.
Professor Richard Lyon, associate medical director of Kent, Surrey and Sussex air ambulance, said: "Time is critical in saving a person's life or reducing long-term disability, and often we have limited information from bystanders about a patient's or multiple patients' injuries to make decisions.
"Callers usually aren't medically trained so information isn't always accurate.
"Being able to see the scene of the incident, not only the patients, but how many cars are involved for example, is game-changing in helping us decide what additional resources we might need to send, assessing who we might need to treat first or what medication we might need to give."
GoodSAM, an app which alerts off-duty medics and those trained in life support to emergencies nearby, was co-founded by Professor Mark Wilson.
He said the new technology is "unbelievably simple" to integrate into existing systems and believes it could be used across emergency services in the UK.
Professor Wilson said: "Being able to see the patient and the scene without them having to download a video chat app, and getting a reading of their vital signs, dramatically improves remote assessment of illness.
"This can be through visualising the mechanisms of injury, for example the number of vehicles involved, or how sick a patient appears.
"This information can radically improve resource management - prioritising patients who otherwise might not have been thought of as that urgent."