A bit about everything: Gaggia Classic. Controlling temperature using PID.
Espressuino - DIY PID, Bluetooth and Preheat Coil on Gaggia Classic - CyberElectronics
Amazon.com: PID Kit for Gaggia Classic Pro for Brew & Flow Control, Pull $2000 Quality Shots with your Gaggia, Pro-Level Espresso Upgrade Kit, Gaggia Classic Evo Pro Kit Only, Machine Not Included (
CoffeePID - a generic PID controller for coffee machines — 1024kilobyte
Adding a DIY PID to the Gaggia Classic Pro - Rambling...
PID Retrofit KIT for Gaggia Classic - European Model RI9403 [KIT-GGX-EU] - $149.50 : Auber Instruments, Inc., Temperature control solutions for home and industry
Gaggia classic PID or new machine? | Coffee Forums
DIY PID and Preheat Coil on Gaggia Classic | CyberElectronics | Flickr
DIY PID on Gaggia Classic | Arduino based multifunctional PI… | Flickr