These units have a serial output, so just need a single one wire interface to read the results from the sensor!
You can find a great tutorial here
AM2302 DHT22 Digital temperature and humidity sensor module
AM2302 Humicap digital temperature and humidity module is a digital output signal containing a calibrated temperature and humidity combined sensor. It uses a dedicated digital modules capture technology and the temperature and humidity sensor technology to ensure that products with high reliability and excellent long-term stability. Sensor includes a capacitive humidity sensing element and a high-precision temperature measurement devices, and with a high-performance 8-bit microcontroller connected. Therefore, the product has excellent quality, fast response, anti-interference ability, high cost and other advantages. Ultra-small size, low power consumption, signal transmission distance up to 20 meters. Making it the best choice for all kinds of applications and even the most demanding applications.
HVAC, dehumidifiers, testing and inspection equipment, consumer goods, automotive, automation, data loggers, home appliances, humidity regulator, medical, weather stations, and other related humidity detection control.
Size: 40 * 23mm
Voltage: 3.3V - 5V
Port: digital two-way single bus
Temperature range: -40-80 Celsius ± 0.5 Celsius
Humidity :20-90% RH ± 2% RH
Platform: Raspberry Pi 2 / B+, Arduino, Intel Edison, Any Microcontroller
1 x temperature and humidity sensor module