This Ultrasonic scanner is made by Devantech that has a longer range than the SRF04.
This great sonar ranger from Devantech offers an amazing wide range from 3cm to 6m. Unlike the SRF04, the SRF08 is interfaced using the IIC/I2C bus. There is an additional photocell sensor on the front of this detector.
This is a bidirectional level shifter used to step down or up signals from 1.8V to 5V range.
A master battery disconnect switch is a lever-operated battery cutoff switch that will disconnect power for the battery circuit.