I was looking at that exact one, plus the 1.5GHz Nano-ITX too. They are certainly small enough. My robot enclosure is 16.5 inches by 9.5 inches, I could fit a MicroATX in that space. There are some Jetway motherboards in MicroATX that could take a green 2GHz single-core AM2 cpu (45w) I have on the shelf. However, with the Jetway MB and fan I am up to about 65watts. A far cry from the PicoITX you mentioned at 14-18watts (idle-full) @ 1GHz.
I also need wireless network. I guess a 802.11g usb key could work with the Pico-ITX.
Here is a ZOTAC GF8200-C-E Mini-ITX that takes a AM2, It also has integrated WiFi. It idles at 30watts and max cpu+gpu at 90watts for a dual core 2.5GHz (45watt cpu)! Thats pretty good, and MB is $120.http://www.silentpcreview.com/article902-page6.html
The Zotac GeForce 9300-ITX WiFi, takes a a 65W TDP dual-core, idles at 35watt but peaks cpu+gpu at 65watt! I dont really get that, it's a 65 watt CPU, so the MB doesnt take any power?
But, the reviewers process is good.http://www.silentpcreview.com/article943-page5.html
I think I am down to the Pico-ITX and one or the other Zotac. If I can find the right batteries to power the Zotac than it is the most bang/buck. I think that is where I will look next. For 4 hours operation, I need about 16Ah batteries to power the Zotac if I expect 50watts avg usage.
I was thinking, since the video will not be used, that I could use the graphics GPU to process AI data. Implementing a shader to calculate perceptrons or something from texture input data. It shouldnt be that difficult and from what I know from a little shader programming it fits the capabilities of a GPU well.