I've tried the Fireboard Pulse as well as the Thermoworks RFX. Both had issues and didn't come close to the "specs" listed on their site. I ended up sending both units back.
Fireboard Pulse - I liked these the best paired with my Fireboard 2 Pro. The App and Controller work flawlessly. Of my two units, one died. They replaced it without issues. The replacement unit didn't work so I ended up sending them both back. The "ambient" sensor was certainly off compared to the true ambient temp in the pit. The only other downside to the Pulse was the weight of the ambient sensor. It had to be placed strategically in the protein due to the depth of the sensor. This could cause issues in some situations.
Thermoworks RFX - I bought the two pack of the RFX units. The small size of these probes was awesome. Fit in any piece of protein without issue. However, one of my units wouldn't hold a charge. I was shocked at this next revelation. I setup the RFX through the Thermoworks app using the "Anonymous" login. When I spoke to the Thermoworks customer service guy and provided my unit ID he could see my name, location, and all the other details. This was NOT COOL in my opinion. I struggled with these RFX units holding a charge for the length of time stated by Thermoworks. I changed all of the settings Thermoworks suggested with no beneficial results. I ended up deleting the app and sending the RFX back for a refund. One additional consideration, these do not work through tinfoil. I could get them to connect to the RFX unit through my KK and 3/8" offset but not through tinfoil.
In the end, I decided to sell my Fireboard 2 Pro, Pit Viper Fan, and all of there electronic cooking equipment. I'm done. I bought my KK to not deal with controllers, extension cords, etc. I wanted something simplistic and reliable. Adding these electronics just creates more headaches. It's so much better not having all the "stuff" when I relax and smoke some meat over the weekends.