This great sonar ranger from Devantech offers a wide range from 3cm to 3m. For further range see the SRF08. The SRF04 is interfaced using the one output line to ping the sensor and an input line to read the echo.
The MaxBotix low voltage MB1010 LV-MaxSonar-EZ1 offers very short to long-range detection and ranging, in an incredibly small package with ultra low power consumption. The MaxSonar-EZ1 detects objects from 0" to 254".
This is the SRF05 Ultrasonic ranger made by Devantech. The Ultrasonic detector can detect from ~4 inches to ~13 feet.
This is the chain and sprocket kit for the IG42-DB4 robot platform. It includes 10 tooth and 15 tooth sprockets, 5 feet of chain, and 4 connecting links.
This is our affordable PWM motor controller. It has three inputs: INA, INB, and PWM. It uses the VNH3SP30 driver. And it have a 5V 1A Output voltage regulator.