CM15A does not have an ActiveX control? That is the reason I started with their controller. I coded support for it in minutes. It was such an easy product to work with. Even with the ActiveX control from Insteon, it is 1000x more complicated that the CM15A's ActiveX control.
Now now... I am not bashing, I have dropped support for the CM15A and only use the Insteon controller now. It is a far superior product. But if you are new and want to code support for X10 in an app, I can recommend the CM15A, but when you get more experienced and speed and reliablility matter, you will want to abandon it.
I'm not sure what all this application controls on the Windows platform, but I do know it supports exactly what you are talking about for the Mac so there probably is a Windows solution. Might be worth looking at.
I know a few people who have used this with Perceptive Automation's Indigo for OSX and it reportedly works great. Most, I think, were using bluetooth phones but the Salling Clicker web site shows support for the Palm TX in Bluetooth and Wi-fi.