I built a HERMS system using a 10-gallon water cooler, a pump, an immersion chiller in an 8-gallon stainless pot with a water heater element controlled by an STC-1000 activating a relay to turn the 240 V element on and off. It works great and was a lot of fun to build.
The down-side is that it takes longer than infusion, even multi-step infusion. I control the water bath temp to not more than 5F above the target mash step so I don't denature the enzymes - that may be overly cautious and it adds more time. It seems to work especially well with unmalted and incompletely modified malted grain. Efficiency is five-to-ten percent higher that single-step infusion - for me.
So, I'm a convert - occasionally. Most of the time I do a single-infusion, no mash-out, no sparge mash. I'm also doing low-alcohol (session) beers almost exclusively, so I'm hoping the rumors about no-sparge brewing producing maltier beer are correct. (Detour: I've been verbally flogged for not doing two otherwise identical brews and comparing them in a triangle test to definitively confirm or disprove that theory. I've elected to ignore that statistically flawed advice - it would take a large number of such comparisons to produce a real indication that there's a difference. Pardon the detour.)
I often use the HERMS system to maintain mash temps while recirculating to produce clean wort - which a few dozen trials MIGHT indicate improves the finished beer.
Sneezles' idea of using a big coffee pot works fine if you can stuff your IC into it, unless you worry about denaturing enzymes in the water bath.
As jmck asked, "...how much do you want to geek out?"