The LF Audio HPVM-PRO is a graphing voltmeter built for automotive and car audio builds, monitoring four voltage sources at once with accuracy to two thousandths of a volt. Its 2-inch TFT HD IPS LCD shows up to 65,000 colors, and the free AuralSync app lets you pick a gauge face, set voltage ranges and colors, and calibrate the meter to your own multimeter.

A solid aluminum case with high-density internal supports and a gold-plated ENIG PCB stands up to vibration, humidity, and temperature swings, while Deep Sleep mode draws just 167 milliwatts and can take up to 294 days to deplete a fully charged 100 amp-hour 12V AGM battery. The Competition face holds the lowest voltage of each hit, and the Pro can even show the voltage of each cell in a 4S lithium bank.