I watch the futures in the morning to decide whether to get in, and often just end my dat at the end of pre-market. It has been pretty consistant to just watch CNBC and hit a few websites to see what their initial reaction of todays trend will be. But once the market opens, I have really no clue. My Fidelity doesn't have futures on it that I can tell. So, if I had a futures realtime subscription from a site, would that give me a few minutes, or a minute, or a few seconds heads up on where an equity will be seconds later, or do they go up and down together?
Absolutely! Look the futures / fair value ratio, very negative values can give you early warnings of an impendig correction, even before the market opens. Once the market opens, futures basically follow the stock/index trend. You dont need a suscription to follow futures/fair value, it's freely available in the internet.
Yes, but not full time. You should know what and when to watch, otherwise you'll get another "noise" indicator. Try to distinguish a few pivot moments per day and watch only at these times.