Jeff, I don't think we are going to find something off the shelf. In the pics below you will see a automotive sander/polisher. We use them because they are variable speed and can be slowed down. Pics are of quarry cut stone as it comes. Unless you pay for Factory diamond cut thats the way it arrives and this is the "good" stuff.
I'll post a few more pics to ahow the effect we are trying to acheive over those posted here:
A few piers
These stones are not fully "pillowed".. in fact not even 1/2 pillowed. We just went for about a 1/2" radius on the edges to clean the wall up a bit.