As
Dave_x10_L suggests, AHP and the CM15A do work, but getting a system fully functional oftentimes requires, and I quote, "Many known modifications and work-arounds". This is where my somewhat cynical response comes from. In my experience, various challenges have turned X10 into more of a hobby than a plug & play solution. But it's a FUN hobby!
The RF range of the CM15A is notoriously poor. However, there are various well-documented hardware mods (from very simple to somewhat complex) to greatly improve this. Similarly, macros are sometimes unpredictable, and adding things like time delays can make them work without explanation. (Search the forums for details.)
The CM15A requires a computer connection only if you are using the OnAlert plug-in to interface with security modules (like the MS10A or the DS10A). Otherwise, you
should be able to load all of your macros to the CM15A and run standalone.
By all means, dive in, but do so with the knowledge that there's usually more effort required to make it all work than the flashy X10 web ads would have you believe...