to be able to call emergency services, is something at which a mobile phone is rather good
Well, that "be able to call" thing is the key here. You might not be able to make a call after a crash.
Generally it's a good idea to have a system that calls automatically for help after a car crash. But the system must be made in a way that it cannot be misused. Unfortunately most of these emergency call systems connect to the CAN to acquire things like vehicle speed and airbag status.
There is a lot of useful information available there, but unfortunately it is a completely unsecured bus. The control units accept pretty much every input sent to them via CAN, so it is really playing with fire to connect it to the internet. I have the same concerns for the new "Usage Based Insurance" systems. These things are just waiting to be hacked.
It sounds hysteric, but effectively you can mis-use these systems by checking the driving situation of a particular person and at the right moment send a torque demand to kill him or her.
Paranoid - perhaps, but I'm pretty sure there are people in the wild wild web who would be more than happy to anonymously kill others.