I have a stoker Wifi that I use for the WSM. It's great! it holds temp +/-1 degree once it locks in and really easy to use. Set to 250F- locks in on the money:
Stoker is pricey for sure, but they are most frequently sold used on the bbq-brethren. It seems that whenever someone puts a wtb ad up there they find one soon enough.
I paid $170 for a like new non-wifi Stoker with one probe and 5cfm fan last year, and then I paid $375 for a used wifi one with 2 25cfm fans (Huge monster fans), 2 pit probes and 4 meat probes this year.
Excellent customer service from John and Rock's BBQ too, but others find them hard to reach at times. Here are some things for you to consider:
-What cookers will you be controlling? I've used a 5cfm fan on my 14.5" WSM up to my 22.5" wsm. As long as you get it up to temp first and you don't use it in freezing temps a 5cfm should be fine.
-Do you need a digital readout? If not, a Pitmaster iq110 is excellent bang for the buck.
-Do you need to control more than one cooker? Then a higher end guru or Stoker may be for you.
-Do you need portability? The pitmaster iq and Guru partyq runs on batteries. You will need to rig up your own power source for the plugin ones if you need them to go without a plug.
-Make sure that your power supply is rated for 220v.
Here's my recs:
Simple and portable for one cooker: Pitmaster Iq or Guru partyq
Single cooker, digital readout, higher fan cfm for larger cookers: Guru digQ dx2 or auberins (better value imo)
Multiple cooker, wifi, datalogger, whiz bang: Guru CyberQ wifi or Stoker Wifi.
For the best: Stoker. My biased opinion of course.