Under Pennsylvania state law, you cannot dispatch observers from one precinct to another to monitor voting. This prevents scenarios such as white observers from one area of the state traveling to a black neighborhood to monitor and potentially intimidate voters.
The state Republican party filed a motion in court to open up statewide monitoring, but they were denied by a state judge this morning.
"Any intervention at this point risks practical concerns including disruption, confusion or other unforeseen deleterious effects," [Eastern District of Pennsylvania Judge Gerald J. Pappert] wrote. "Plaintiffs waited until eighteen days before the election to bring this case. ... Were the Court to enter the requested injunction, poll watchers would be allowed to roam the Commonwealth on election day for the first time in the Election Code's seventy-nine year history — giving the Commonwealth and county election officials all of five days' notice to prepare for the change."
You can probably add this to the list of things Republican will fight in courts and state legislatures over the next four to eight years. I also expect they will make another push to eliminate early voting in other states (Pennsylvania doesn't have early voting).
Once the voter ID canard runs its course or is ultimately unsuccessful, they will try to find new ways to suppress voters.