http://www.littlepc.com/products.htmWith a USB MIDI pedal and a DIY preamp to drive the Line input one of those things is basically what you're talking about. So it stands to reason that if you bought an SBC similar to what is packaged in the Stealth package and added the Line input preamp, then packaged it in your own custom enclosure, and perhaps with a USB LCD display plus pushbutton pad (like MatrixOrbital has) then you would have just what you are talking about.
Recently I have been contributing code to this project:
http://rakarrack.sourceforge.net/You really need to try a current release (0.5.8 Equinox) or build from current development sources to appreciate its value.
We are in the process of discussing UDP or TCP/IP service for controlling the parameters in headless mode. Then you could write an app on your iPhone to control the program. A SBC would lend itself nicely to this kind of application. In all reality, a netbook mounted in a rack may be the no-brainer way to do this. If I had money to make my "dream" setup, it would be a rack-mounted high-octane computer with a touchscreen monitor in a ~10U rack.
These days my stompboxes live in a basket on a dusty shelf. I have a USB audio card, my laptop and the Behringer FCB1010 MIDI controller and Debian Linux. Primarily I use Rakarrack simply because I know it intimately... and it is truly versatile...but also is PD, Guitarix, Calf Audio Plugin Pack, all kinds of LADSPA, DSSI... really is amazing what software is available for free and some has very top-notch performance and DSP practices (like Calf... K Foltman is a genius). VST only represents the most well-known standard for software DSP, but really anything that uses jack on a realtime kernel is a great platform for embedded processing. "VST" is getting to be like Microsoft Windows where most people aren't even aware that there is such a thing as an alternative.
I hope to pull out my soldering iron again & do up some great analog stompboxes when I get my fill of digital experiments...but the digital domain really gives me a place to quickly prototype ideas and do experiments. I can make digital "virtual distortion pedals" for instance, then use the same filtering & tone blocks implemented in an analog circuit if I like the digital unit...
This seems like a possible board:
http://www.axiomtek.com/products/ViewProduct.asp?ptype3=183&pos=2&ptype2=205&ptype1=202Also winsystems has some good SBC's based on the Intel atom:
http://www.winsystems.com/index.cfmWith a Linux distribution, this is actually really easy to implement. You make a bootable USB stick and you can even boot off a live USB image and don't really need to install if you don't want to. Dumping the image on a flash card for these systems is really not a highly technical task, either.
I also have discovered this project:
http://sourceforge.net/projects/gnuguitarinux/files/lightweight debian + fluxbox system ready to fly for a live guitar processor.
My general assessment is if you already have a netbook, laptop or old PC there is no good reason to spend large amounts of money on commercial hardware FX...for most people.