okay I decided to do the logical thing and research the power flash module. It's amazing what you can find out if you look! As you already know, and I now know, the power flash unit transmits while the universal unit receives... So basically what you're doing is using the power flash unit to turn on another X10 module and then have your computer tell you through macros that that module is on.
Yes. My Powerflash address is F1 and the magnetic door switch is connected to the Powerflash terminals. When the garage door is lowered, the the Powerflash sends "F1 ON" and the computer announces through wireless speakers around the house "The garage door is closed". Obviously you can reverse your logic by the installation position of the magnetic switch on the garage door frame. In my home control system, the F1 address is labeled "Garage Door Closed"
I don't bother repeating the "Garage door is open" message but that would be easy to do with flags in a macro. Other users have also set a lamp module etc. to the Powerflash address so when the door is up, the lamp is ON, indicating the door is open. In this instance you would want the door switch to the Powerflash to close when the door is opened. An advantage to this (having a lamp set to the Powerflash address and installing the magnetic switch to be closed when the door is open) is even if you home control system is down, you would know the door is open.
X10 doesn't advertise the Powerflash or the Universal module much, but these modules can act as the I/O for non 120V home automation.