well I'm really not familiar with what's available (and not available) for macs... but I think your best bet for making smooth lines in photoshop would be using the pen tool. In the version I use (photoshop CS2) there is no function for stabilizing pen strokes, but there might be in newer versions. I'm not too sure
but to my knowledge, the pen tool is the only way to get perfectly smooth lines. I also have an older tutorial on using the pen tool here if you're interested:
[link] (click download image to see it)