This method was promoted by Cook's Illustrated at one point, not that they invented it. Basically you put the steak in the oven on the lowest setting it will allow, and wait until you get 100F. Then you sear the heck out of the surfaces, over maximum heat, and you should be right at the rare/medium-rare point. You can also do the reverse: sear the bejeepers out of the surfaces, and then roast at medium temperature until the inside is where you want it, which is a faster system -- but remember there are times when you'd prefer slow.
1" is about the minimum point where there's any reason to do this. In high-end pro kitchens, as far as I am aware, this kind of method is used when cooking something like a chateaubriand or côte de boeuf, which can be easily 2" thick and would be in serious danger of drying out or burning horribly if you did it entirely on a surface grill.
My feeling is that one should learn to cook a normal -- let's say 3/4" -- steak on a grill or pan. Learn what the different levels of doneness feel like. Use this kind of method when dealing with something definitely abnormal, the sort of steak you're going to cut into portions before serving.