http://www.8devices.com/product/3/wi-fi-4-thingsYawn, Yes I know, Yet Another Wireless Networkdevice.
Another Linux SoC module (Yawn again)
The thing here is the price, at around 22 Eur for the core module it is close to Arduino prices.
It contains a mips processor of about 200-300 MHz and a 32 MB RAM + 8M Flash.
What got my interest is also that it got Wifi, ethernet and USB (think 3G dongle!) also some general purpose I/O legs are available.
It just might be possible to squeeze the bitcoind into it, making it a very cheap autonomous bitcoin interface.
The main reason for being affordable is probably that its based on the RT3050 chip, used in large volumes in cheap wifi routers.