If you're paranoid about these things you could keep a DC voltmeter plugged into the cigarette lighter. (Saw one at Wal-Mart for around $12.)
It would give you a little warning if your voltage dropped drastically.
The two times my voltage regulators failed I either wasn't looking at the meter because it was night time (SD on a long trip) or I didn't have one plugged into my wagon.
The ABS light comes on when you get below 10 volts, but by then it's almost too late...

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Bob Roe
Lehigh Valley PA USA
1973 Olds 88, 1972 MB 280SE, 1978 Datsun 280Z, 1971 Ford T-Bird, 1972 Olds 88, 1983 Nissan Sentra, 1985 Sentra, 1973 230.6, 1990 Acura Integra, 1991 Volvo 940GLE wagon, 1983 300SD, 1984 300SD, 1995 Subaru Legacy L wagon, 2002 Mountaineer, 1991 300TE wagon, 2008 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon, all gone... currently
2007 Honda Odyssey Touring, 2014 E350 4matic