I don't know what the record is for installing Zoneminder on the cheapest and lowest wattage device, but it seems the Seagate DockStar would be a contender.
For reference, the Seagate DockStar is a Pogoplug device running at 1.2 GHz with 128 megs RAM, 3 USB ports, and it can usually be bought for about $30 US (mine was $25). It uses about 5 watts of power and it's easily hackable. In a few minutes you can have Debian booting off a flash drive.
Anyway, for others interested in running ZM on the DockStar, I thought I'd share my experience. Thanks to everyone who contributed to the threads linked below:
1) Installing Debian Lenny. These directions worked perfectly:
http://jeff.doozan.com/debian/install_lenny.htm
2) Installing Zoneminder. I had some trouble getting it working with apt-get, so I compiled using these instructions, which were almost perfect:
http://www.rmacd.com/howto/zoneminder-d ... nstall.php
Note: I also ran into this (easily solved) problem during compilation:
http://www.zoneminder.com/forums/viewtopic.php?p=56386
3) After finishing the installation, ZM wouldn't display any video from my remote camera. After some debugging, it seemed to be a shared memory issue. Implementing the following memory tuning solved the issue for me:
http://www.zoneminder.com/forums/viewtopic.php?t=9692
After that I had to make a few minor changes here and there like timezone and startup commands, but it seems to be working. The web UI is pretty slow, but video streaming seems reasonable and the load seems under control (with a single remote DLink DCS-910 camera). I'll need to test some more to see how reliable it is, and I'm not sure how long a thumbdrive-based always-on Linux system will last, but it's fun use for a cheap gadget. And who knows, maybe it'll allow me to retire my always-on environmentally unfriendly desktop server.
Cheers,
Aaron