Sensirion SHT1x/SHT7x precision humidity and temperature sensor (Octopart search, starting at $25). The SHTxx has a two-wire serial interface that requires pull-up resistors (R1,2), values between ...

If you’re going to develop another Arduino-compatible board these ... dubbed the “Ambient Board”—is a buffet of sensors: temperature, humidity, CO, NO2, light intensity, and a microphone ...