You know, most people would be lost and wouldn't know what brand to purchase without some help. There are so many "cheesy" take-offs on decent switches and sensors.
The XTension List at http://www.shed.com is dedicated to Mac X-10 automation and related geeky things that you'd ever want to do.
Some other applications may already be OS X compatible but, there's no comparison to the quality of XTension and the list members who come from all types and backgrounds... and probably have already made the mistakes that cost you money. Why make expensive mistakes? Just join the list and you'll see why most Mac HA people choose XTension instead of the copies...