UPDATE: I've received the electronic temperature controller from ebay and tested it out with my analog crockpot and it works pretty great as a sous vide machine. (See photos)

The PID temperature reading is accurate, and you can also calibrate it if necessary. (+-3.0 deg)

There is a bit of temperature fluctuation to be expected when using a crockpot, up to +- 0.5 deg (C) on 'low'', because the crockery continues to emit/absorb heat even after the heating element turns off/on. However, that's more than good enough for me. 63 degree eggs turned out perfectly runny, 64 degree eggs turned out with a nice yolk that barely holds together, and 55 degree salmon was lovely, although it could benefit from a couple of degrees less heat for a creamier texture.

Critiques:

1) When it came the contacts in the socket were not 'tight' enough so I thought it was broken. I just needed to tweak the contacts (without opening it up, and without powering it up) with a tiny screwdriver to make them contact my crockpot's plug better. Works fine now.

2) There are a lot of detailed settings to play with but only 4 buttons, so you really need the manual to figure out where you are in the menu of options. The manual is in decent english. But once set, you're good to go.

3) You must either set the gadget to work in 1.0 deg increments OR 0.1 deg increments. So if you want accurate control (eg set the crockpot to start heating when temp falls by 0.1 deg below target), then to set the target temperature you have to use the up/down buttons to scroll to the desired temperature in 0.1 deg increments. A little bit slow if you need to change the temp by more than 10 degrees, but you can just hold down the button as it scrolls up/down.

All in all, not bad for a $23 gadget! Would buy it again any day over a $200 immersion circulator.