This is becoming ridiculously frequent. I predict automakers will have to get together with infant car seat makers to come up with some kind of alarm system.
It would be easy to do. Pass a law mandating that baby seats of all types be fit with a wire harness socket. All of the seats would have mating sockets. You can't operate the seat (the buckle won't work), unless the seat is plugged in to the socket.
If the key is out of the ignition for more than three minutes with the buckle still in the slot, the windows roll down automatically, and the car's alarm goes off. You can even program the car (in new models) to call your cellphone or pager if that condition exists.
It would be a real enhancement.
I doubt that it is any more frequent than it is more likely to be reported as news than before.
Certain stories are programmed as keywords and flagged by "readers" for wire pickup.
I'm working on that now. It's based on a pressure sensitive switch. If there is more than 3 lbs of pressure on the car seat fifteen seconds after the engine is turned off, the alarm will sound. Still some bugs, but I will have it worked out soon.
Or, we could just get rid of the federally-mandated exploding airbags, so the kids could ride in the front seat where they belong (where the driver can see and reach them).
That's actually a very smart idea. You should consider developing it further in some way.