Looking through the two projects and trying to figure out the differences. Would the TeensyNet project take place of the individual Arduinos in the BrewPi system? Or are they very different projects that work independently of each other?
I have not looked closely at the BrewPi project, but it appears that there are a few differences:
The BrewPi RPi appears to communicate with the Arduino via a USB connection, requiring some setup for each additional Arduino.
The TeensyNet is connected to your intranet and discovered by the RPi using zeroconf, so finding new TeensyNet boards is as simple as telling the main page to search for them.
It appears that one Arduino is needed for each set of thermometer/Switch combos in the BrewPi.
The TeensyNet can support up to twelve thermometer/switch combos ( called "Actions" ) per board, with multiple TeensyNets monitored and controlled by a single RPi.
It looks like the BrewPi only supports DS18B20 Digital Thermometers and DS2413 Switches.
The TeensyNet uses the DS18B20, DS2406+ switches, MAX31850 K-Type Thermocouple Readers, with more to come.
I've also created a 1-Wire Slave Emulator Board that can be used to connect non-1-wire devices to the 1-wire mini-lan that the TeensyNet uses to monitor control the devices.
Adding the DS2413 would be a trivial exercise.
The BrewPi uses Python on the RPi side, the TeensyNet uses PHP. Pick your poison
It appears that The BrewPi uses Amtel Studio, which appears to be Windows-based. The TeensyNet uses the Arduino IDE supplemented with the Teensyduino add-on which works with Windows, OSX or Linux.
The BrewPi uses the Arduino. The TeensyNet uses the MUCH more powerful and capable Teensy3.x