This is for Matss (re: garden Temp
control.) I would suggest looking at the
Parallax stamp microcontrollers.
parallax.com) You can use an analog temp.
sensor, an 8pin A/D converter, and a
microcontroller to handle the processing
AND generate the X10 command to a powerline
interface. (They have some great project
books and a link to projects and code
contributed by viewers..) I'd be willing to
bet you would be able to modify an existing
project there to fit your needs. Hope this
helps..