You could do it pretty easily with an Arduino and a large servo for flipping the tank over. You'd be looking at investing in a lot of plumbing and annoying mechanical stuff if you wanted the controller to automatically fill and dump the chemistry at the correct time. If you're interested in it, I recommend dropping $20 on eBay for an arduino and having a play with it.
I use the Arduino to implement my (there was a url link here which no longer exists).
If you want a machine to agitate while you watch TV, a Jobo is a really good start. It doesn't support (semi-)stand development though, only continuous agitation. On the upside, it can use much less chemistry if you like using undiluted solvent developers.