The Hook by Power Probe is both a diagnostic tool and electronic circuit tester that works on 12-48 VDC systems.

The Hook powers large loads up to 100 amps and features power-up components, measures amps and ohms, calculates resistance, continuity relay tester, jumper lead, voltage reference, supply mode, voltmeter, voltage indicator, audible feature, bad ground indicator, finds short circuits and has an adjustable circuit breaker.
For more info: powerprobe.com.