Well, OnStar isn't worldwide in coverage but the technology is there. They'd have to have a lot of satellites to cover the whole planet and then you have to equip all the ATC centers. It probably comes down to a cost-benefit analysis. We're making a big deal out of this event, and yes it is terrible, but this type of accident is exceedingly rare. The cost of maintaining a new tracking system would be passed on to the passengers.
As for the OnStar thing - I was surprised to see large areas of Texas, Wyoming, and Kentucky are dead zones for it. Look here