I found some modules made by Olimex that hit the sweet spot for me.
They haveboth motion and temperature sensors on them, use both PIC microcontrollers, and use a Zigbee network for wireless communication.
My plan is to add a small solar panel (2″x2″) to recharge batteries for the outside mocules. I’m not quite sure how I will power the inside modules.
Anyway, these modules are programmable (if one knows PIC microcontroller programming). I holpe to be able to put them to sleep for power savings, and wake them up once and a while to read the temperature and maybe sense motion. Ok, I may put them to sleep for 1/2 a second but it still can lead to good energy savings.
My plan is to learn how to program these, probably extend them for additional I/O (reading additional temperatures attached to a given module) and begin building a network of maybe 20 temperature sensors. I will create code that will poll them, log the data to a database, perhaps make that data available for real-time graphine on the web, but most importantly, learn things about how my house responds to temperature changes to both optimize energy savings and to devise logic to save energy.