EAP86
Perhaps SFARP has not replaced ALARP in the UK, but it has elsewhere. In Australia the new WHS legislation makes a big thing over SFARP, and is leading to a lot of time and effort to prove we have done everything reasonably practicable, with requests for details of what mitigations we didn't implement and why not. There may be an engineering interpretation of the term , but there is also a legal interpretation which concerns me.
I'm glad you brought up grossly disproportionate, I didn't want to mention it originally as it would muddy the waters in terms of how you decide you have reached the ALARP/SFARP point.
There is at least one health and safety legislative act currently in use in the world that defines what "reasonably preacticable" is, and grossly disproportionate is only one of the factors to consider. As for the cost of implementing a mitigation, the insurance industry uses the term "cost of preventing a fatality" which in effect puts a monetary value on a human life.
One side effect of this case will be that companies who produce products (and I do mean anything) will need to spend more time and resources providing evidence that they have met SFARP, so that in the event they are taken to court they have a justification for doing what they did. Not much of an issue for your new smart phone, but aircraft, ships, trains, land vehicles all have a greater potential to cause death and injury.
And don't forget driverless cars!