I'm looking into building an automated RIMS system. I think I understand the principles pretty well, but there is one sticking point for me. Since the heating element is container in the pipe, I would assume that you have to heat the original volume of water necessary for the brewing, before you add the grain. So how is this done? do automated RIMS systems usually have an extra hot water res that holds some of the pre - heated water, and then a a series of valves are triggered? I would assume the same is true for the sparge water. You need to add water to the system during the sparge, so where does that water come from?
For the mash liquor, you could do the strike-temp heating in the mash tun through the RIMS tube before adding grains, and then RIMS to hold/change temp. The sparge liquor is going to be a problem, though; without a second vessel, you'd need to add cold sparge liquor, then RIMS-heat it up to sparge temp, which probably isn't going to do great things for the mash (though I'm not sure of the actual effects).
One alternative would be to try to do a "no-sparge" full-volume RIMS setup, with a sufficiently-large mash tun and corresponding efficiency impact.
I've also seen two-vessel setups that basically use the boiling kettle as a liquor tank, then recirc between the kettle and mash tun, effectively looking to "equalize" the sugars in the liquor between the two vessels during the recirc before fully draining the mash tun and commencing the boil. Though it appears to be more of a HERMS setup, Sean Coates has a great diagram of such a configuration and process: Scoates two-vessel diagram http://caedmon.net/2-vessel_brewing.png