MD..never really thought about what the EMT's did but i assumed they did more than give O2, fluids and transport.

Many have been known to splint fractures and stop bleeding, but transport to a competent ER is critical.

It depends on the country, but in most the police are in charge of identifying persons. I guess thats why the taxdisk ID was a suggestion from the police. Not sure how much easier it would make since, you they can just look in the database for the registered owner.

Not sure what EMT's and paramedics are allowed to do. The medical skills and training varies a lot in countries. From trained volenteers, to nurses to docters. Some can give very advanced procedures on the spot.

Depends where you are ...
In the US, EMT-Basics are basically first-aid only. Splinting, O2, transport, bleeding control. Very few medication, glucose is OK, oxygen, sometimes epinephrine or albuterol for asthma.
EMT-Intermediates are fading away in most places. Usually first aid and can do some limited IV fluids.
EMT-Paramedics have about 40 drugs, can intubate, defibrillate, start IV's.

I've never heard of blood being carried or transfused in the field by EMTs. That being said, I know a doctor in NJ that, during his EMS fellowship, was doing on-scene blood transfusions. Again, this was a physician, not a paramedic or EMT.

And as Tjin alludes to, EMS doesn't ID people. Usually the PD, rarely the FD.

Why would you leave your house keys in your car?

They suggest including photos to help with identification. Also, the main information is next of kin, which is likely to be the same, or close enough, for all drivers (assuming it's a privately own vehicle and not a car pool business one).

In the UK the license plate will only give the address of the registered owner. It doesn't include any phone numbers or anything about the next of kin. It doesn't include a photo, either, and the registered owner may not be the driver.

A neck tag is fine if you like that sort of thing, but many of us don't like wearing stuff around our neck. Also, I'm not sure how effective it would be. Often first responders are reluctant to go ferreting through your personal possessions in case they get accused of theft. The windshield thing is supposed to be easily visible, obvious in intent, and accessible.

I listen to Police and Fire on my scanner every day.
Here with a name they can bring up possible people and with DoB can narrow it down. Then they can find vehicles you own, address you live at, SSN, phone numbers, outstanding arrest warrants and protection orders and the last time a police officer contacted you. I wouldn't be surprised if the driver's license picture could be passed on the mobile terminals for positive ID.

Sometimes they'll pass the last 4 digits of the SSN over the air to confirm the correct person (which is why I chose to put my SSN on my tag)

If you have keys in a bag and jump out of the car quickly to get something, pay for gas, etc.

During vacation I often store my house keys in the car in a little key safe. No point in taking them along while mtb/climbing/hiking, etc. The tent certainly isn't very secure and bringing my keys along means i can bent them (happens...) or loose them.

Hmm... good intentions by a bureaucrat, without a doubt. It sure would make you a ripe target for criminals, especially for identity theft, amongst other things. Only would take a broken window or an unlocked car door to lose valuable personal information.

As far as contact information goes, I'm not sure how it is on that side of the pond, but your law enforcement agencies probably have access to nearly all of the data they could possibly want (and then some). Databases are only becoming more and more connected, and a few easy mouse clicks away. And if they can't get it right away, it likely only takes a short bit of follow-up research.

IMHO, what this "Contact Disc" does is make things easier for people filling out reports, forms, and citations.