The role of 'Safety Pilot' shouldn't be taken on lightly. You don't get to log any flight time, but if there is an accident, people will ask 'why didn't you do something?'
I would advise anyone who is contemplating acting as a Safety Pilot to thoroughly familiarise themselves with the medical condition of the Pilot, and be aware what form any incapacitation may take.
Incapacitation takes many forms, and rarely follows the classic chest gripping keel over that tends to spring to mind. The onset of incapacitation is often gradual and can go unrecognised by both the Pilot and Safety Pilot.
At altitude, there should be time for a such a gradual incapacitation to be discovered before it becomes critical, but on final approach, the situation is different.
To guard agains this as Safety Pilot, you may consider asking the Pilot a simple question on final to check for a response. This can be something you pre-arrange with the Pilot, if you think he/she would be receptive to such a thing, or something you just do without them realising it's true purpose.
MJ
