Presto multi cooker sous vide- clarification? I read Marc-André LaFortune's post about using the Presto multi cooker as a secondary sous vide machine.

I'm interested in doing this but it would appear to me that the machine is not accurate enough without modification to hold the pot to +/- .7 F.
Do you do this by monitoring temperature with a thermometer and switching it on and off, or with a PID controller like others have used?
The standard hack is to use a PID controller.  IF you google, you will find many articles detailing exactly how, such as this detailed one from Over Engineered.

There are now also a couple of vendors of moderately low cost circulators intended specifically for this application such as Sansair that you insert into a pot or cooler.  They are new to the market, so there are some early adopter issues being reported, but the idea is quite elegant.