Here is an interesting home automation indication mod.

“Like almost all the currently available UK X10 modules, the LD11 does NOT support status response. This coupled with the fact that X10 commands can sometimes “go astray” and seemingly disappear into the electrical ether before reaching the chosen device, means that the tracking of the current status of a device is very error prone. Intelligent controllers like HomeVision and software like Homseer make a valiant effort to track the current status of devices by listening for the X10 signals on the wire but commands are sometimes not heard or can be misheard and any device that is locally controlled will have its state changed without the status change being announced on the wire. This last point was a real bug bear for me, I just didn’t know if someone had switched on a light by hand.”