Dock Wise Marinco's new GalvanAlert ($150) only communicates via four multi-color LEDs, but they're right where you want them, in view as you plug a 30-amp cable into a shore outlet. Its internal sensors will purportedly tell you instantly if power is present, if its polarity is correct, and-most important-if stray current threatens serious galvanic corrosion. Marinco, (707) 226-9600; www.marinco.com