Octopus Electronic Bricks! You can use them build electronics projects just as easy as piling bricks! By using Octopus electronic bricks, you may connect Arduino or compatible boards easily with various digital, analog and I2C/Uart interfaces. These breadboard-less firm connections includes an extensive collection of modules like potentiometers, sensors, relays, servos, and even buttons. Just plug and play!
This is a Rain/steam sensor from ElecFreaks. This steam sensor can be connected to the Arduino IO Expansion shield directly. The output voltage will increase when the humidity of the sensor surface goes up.
You even could use it as a touch panel.