B737 Captain reported Pushback Crew deviated from pushback clearance instructions.

Narrative

During pushback from gate; we were given the ATC instruction clear to push back; tail North on Whiskey. As the Pushback Crew pushed the aircraft; they started pushing the aircraft tail South on Whiskey. When we got the air he had already started to swing the tail so we had him stop the aircraft while we coordinated with ATC to see if that would be a problem. They said it shouldn't be a problem and they had no worries about any conflict. This also placed the right wing tip fairly close to the service road. The First Officer looked out his window and did confirm that the wing walker was watching the spacing. We paused without moving giving the vehicles that were In line on the service road a chance to go around the wing. When the vehicles cleared we finished the pushback with the tail South on Whiskey. Everything was uneventful from then on. When the First Officer was starting the engines; I called Operations to tell them they should have a Ramp Supervisor meet with that crew to discuss what went wrong. Due to the error of the Pushback Crew; The aircraft was pushed back with tail South on Whiskey; instead of the issued clearance to push tail north on Whiskey.Watching this problem unfold I was struck with the thought; why do the wing walkers not have instant communication with the Pushback Crew? If they would've had wireless headsets they might've discovered the error and push back before I did. That could've resulted in getting the correct pushback direction instead of what we ended up with. I recommend that wing walkers have wireless headsets so they always have a back up communication with their tug driver. Relying on just wants to communicate properly is not adequate. I think a wireless headset that allows instant talking to the Pushback Driver is the right way to go. Both verbal communication from the wing walkers as well as wands should be used together. That would improve safety and be a better way to do it than what we currently do.