One of the major obstacles that D.I.Y. home automators have to face is how to tie-in appliances and other equipment that isn't automation-ready. In the X10 world, there are a number of specialized techniques (see Smart Home Hacks) but they're often Rube Goldberg-esque in their approach.
Smarthome is introducing a new module that promises to blow those old methods out of the water. The new SynchroLinc monitors the power status of any device and sends an INSTEON signal when it is turned on or off.
You could use this, for example, to trigger a home automation sequence when you turn on the TV. Or, have your house respond when the garage door is triggered. What's most impressive is that the SynchroLinc offers a calibration step that should, in theory, allow it to detect power changes in most any device. (Including those that have "soft on/off," such as many AV components these days.)
The SynchroLink isn't shipping yet, but should be available by December. The pre-ordering page says it's a reasonable $40.
If you try it out, please do let me know of your experience. As you can tell, I'm very much looking forward to it myself.