I recently set up a MythTV box in a room where several X10 modules are installed to help set the proper lighting in the room.
First off, if you don't know what MythTV is, think of it as an open-source, free TiVO. If you have the right components for a computer, and you have the right OS and software, you can have a MythTV box giving you DVR capability, even hi-def DVR, for much cheaper than TiVO or your cable/fibre provider's DVR (YMMV, naturally).
I am using the KnoppMyth linux release, which is the Knoppix liveCD remastered into a MythTV standalone/backend installer and a front-end liveCD (meaning you don't need to install it for just frontend use).
There's plenty of documentation about installing and running KnoppMyth, or MythTV in general, so I'm not going to bore you with those details here.
I have an old X10 Firecracker kit, which comes with a lamp module, a transceiver module, a remote, and an serial device known as a CM17A, aka the FireCracker. It's a small black adapter that plugs into a serial port on your computer. I have also installed several X10 wall switches for the room, so that the room lighting as well as a lamp are all controlled by the X10 remote. Lights can be dimmed, brightened, turned on or off. I don't have any appliances but in theory, you could get additional modules, and the sky is the limit (radios, microwaves, gas/electric fireplaces...).
There are three things I want to do to make this work:
1. Get control of the X10 serial adapter
2. Give MythTV the ability to control the device
3. Give my MythTV remote control that control as well
1. A working MythTV system, for TRUE ease of instruction-following use KnoppMyth
2. For step 3, you need a remote control
3. Some linux knowledge.
4. MythTV box needs a network connection to download files. If you can't provide this, download the appropriate files separately and copy to the MythTV computer somehow.