There are some great Sous Vide machines out now, expensive but very accurate. You can make a very accurate tempering bath yourself, that you could also use for Sous Vide cooking, for much less than the commercial ones, if you're handy. Google "do it yourself sous vide machine" for plenty of links. Here's one:

They claim it can be built for $75.

For me, for C-41, I use hot water in an insulated tub (you can use any ice chest). I monitor temps with an accurate (+- .1 degree) electronic thermometer (they aren't expensive). It doesn't take long to work out the starting temp that results in your chems and the bath hitting 38 degrees C at the same time, and once it is there, you just start your process, it won't drop too much before you are done with the critical steps. I also keep monitoring temps, and just add a bit of hot water from a separate jug if I think it is dropping too fast. But actually it never happens.

Results come out just like the pro labs. I do lights out dip and dunk for 4x5, using the Combiplan and some 1.5 liter plastic juice jugs for my tanks. For this, I use a timer app on my iphone that can generate different sounding ticks and alarms for the various processes, and the phone stays under a light trap nearby. For everything else, its lights on with a Paterson tank. Easy peasy.

Oh, and this is all done in a spare bathroom, so I have very easy access to hot and cold water.