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.
This is the SRF08 Ultrasonic ranger made by Devantech. The Ultrasonic detector can detect from ~4 inches to ~30 feet.
This is the SRF05 Ultrasonic ranger made by Devantech. The Ultrasonic detector can detect from ~4 inches to ~13 feet.
This prebuilt compact 4WD wheeled robot platform is equipped with 32mm motors, a motor controller, and Spektrum remote control. This pre-built is a customized version of TP-151-032.
These are high quality sealed Single Pole - Double Through (SPDT) relays. This relay's coil is rated for 24V.