I used PartyQ, didn't like it, too weak for bigger grills and can run wild on a kettle; then a PitmasterIQ 110, it worked well, but I wanted more automation (instead of manually set the damper) and wireless. So I made my own. I started by making my probes faster because all the food probes on the market today are not responsive enough. Then I replaced the PID controller with the Arduino chip, which is open source and more programmable. I was a fan of Marantz receivers, so I used two OLED displays with a big dial coz I thought that was the coolest thing about these receivers. The menu navigation and temperature setup were like the 3D printer we have in the shop (I make motorcycle racing parts for a living), now instead of pushing buttons for dozens of times, all you have to do is click, dial and click.
Geeks make best BBQ!