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I've wanted many times a voltmeter dash gauge, something that used to be standard. A voltmeter will tell you if your charging system is working properly, and if your battery is dying. Having an app do that for you is like firing an 88mm flak gun at a cockroach.

I don't know why Apple cannot vet these apps for transmitting data irrelevant to its stated purpose before they approve it for the walled garden.

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You can DIY this in an afternoon.

Get a red LED from any auto parts store. Connect it to the alternator and the positive battery terminal. It will illuminate when there is a voltage differential. Brighter is worse.

Optionally add switch if you want to prevent full illumination when vehicle is off. Or add a relay spliced into the radio / ignition / accessories circuit.

I never thought of that, it's a good idea.

I do prefer gauges, though! I've installed them before.

One option is to use a voltmeter that plugs into the cigarette lighter outlet. There are a bunch of cheap options on Amazon.

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