I noticed four(?) towers around the SpaceX launch pad during yesterday's aborted launch
img credit NBC News
What are the towers used for? Tracking? Radio communications?
They are used to redirect lightning in the immediate area. This essentially creates a faraday cage, shielding the rocket from being fried by lightning. You can see how high the towers reach, high enough to ensure there is no risk of lightning hitting the craft. Also, since this is a mobile launch platform, it would be safe to assume that the towers have some sort of motorised mechanism to adjust their height, allowing for a wider range of launches.
TL;DR: They're lightning rods.
The big top rods are insulators. Such cages are grounded through wires sloping out to ground points several tens of meters away. Also the ground points are connected to each other by a potential equalization loop. The metal lattices of the towers are grounded too, and also connected to the loop - but they are insulated from the tips, so in a strike they do not act as conductors. There was one such insulator on the top of the Shuttle launch tower. It was a spun fiber in polymer matrix structure, ad the time the biggest such cylinder in the world. The tip was connected to three ground points.