This is QRE1113 breakout board features a digital output, using a capacitor discharge circuit to measure the amount of reflection. This tiny board is perfect for line sensing when only digital I/O is available, and can be used in both 3.3V and 5V systems.
Apply 5V and be shaken by this small, but powerful vibration motor. Works great as an physical indicator without notifying anyone but the wearer.
This Liquid Level Sensor from Milone Technologies is a great way to measure the level of a liquid. It has a resistive output that varies with the level of the fluid. It does away with clunky mechanical floats, and easily interfaces with electronic control systems.