Have you looked at these:
http://www.microrobotics.co.uk/vm2/vm2.html
I've used the VM1 with a touch screen for a lot of commercial machinery (which we sell them but have 27 running here that have been running 24/7 for the last 5 years, never been switched off), never had one fail, they are as capable as a PC and very easy to program (software is free and is a kind of object basic). 8000 lines of code compile to about 20kb and will interface to any thing. The controller on it's own is £57. Has ethernet capability and SD cards, RTC, I2C, encoder inputs, multi tasking etc etc. Even seen one hosting a web site! Bit more Expensive but extremely capable.
Tom