Let's say the critical indicators you're measuring are a human being's "vital signs" (respirations, heart rate, blood pressure, etc.)
We've done this for race-car drivers, pilots, and astronauts for many years now, and equipment that does this kind of thing in a medical crisis is on the back of many (if not most, by now) ambulances. Smart defibrillators, which "interpret" a person's EKG and administer an electric shock to stop dangerous arrhythmias, can be found in mall food courts these days - or you can buy one for your home or office at Amazon.com for roughly the same cost as a Macbook.
Now, consumer-level medical telemetry appliances are about to proliferate. Although I hope for many more years of relatively good health, I am hopeful that when the time comes, I will be able to be fitted out with the nth generation of this gear:
The Bluetooth wireless technology that allows people to use a hands-free earpiece while making a mobile telephone call could soon alert the emergency services when someone has a heart attack, Ofcom predicts.
The communications regulator said that sensors could be implanted into people at risk of heart attack or diabetic collapse that would allow doctors to monitor them remotely.
If the “in-body network” recorded that the person had suddenly collapsed, it would send an alert, via a nearby base station at their home, to a surgery or hospital.
New wi-fi devices warn doctors of heart attacks (Times Online, 7 May 2008)