This does not sound like something well defined, not even the whole idea.
You need to give us the idea on what computer system should be installed in the car and connected to the car equipment. As far as I know, nearly all cars are using the CAN bus, see http://en.wikipedia.org/wiki/CAN_bus
So, the car's on-board computer is connected to the number of car devices and runs some real-time system, apparently. Theoretically speaking, you can replace the whole system and run a Web Service on it. This is highly questionable, even if you are only working at the very rudimentary prototype. Just one note: all Web technologies had never been even close to the real-time, and some reasons are really fundamental, the behavior of the note in the network is fundamentally probabilistic due to the internet protocols.
Most likely, you can say that you are going to use yet another computer
monitoring the acceleration and air bag noise. I say "yet another" because this computer should be attached to the CAN bus as well. I have no idea what CAN controller are you going to use, perhaps a wireless one; I just never heard about such thing. OK, let's say you are connecting to the CAN bus. Still, this is very questionable as the concern is the possible disruption of the car's real-time operation. The problem is: CAN is relatively slow. I was always amazed by the fact how a vehicle can react to the events withing required latency (as all hard real time systems do), but it can. It looks like the embedded system is really licked clean in terms of performance, so any additional host indirectly taking out some extra resources might disrupt the real-time operation.
Please don't get me wrong: I don't say this is impossible. I only suspect that the problem might appear more serious that you might think of by orders of magnitude. :-)