A reliable pay-as-you-go phone

I'm trying to coax my husband into getting one. He often works late and is driving along unlit country roads at night. I worry he'll tangle with a deer or another car on some back road in the dark and have no way to call 911 or me.

What he needs is one that isn't going to cancel his unused minutes if there's no need to use it. This will be purely for emergencies to keep in the car so it doesn't need all the bells and whistles.

Any ideas on a cheap little pay-as-you-go phone that fits the bill? One that has a car charger accessory or that you can buy a compatible one for would be great too. Thanks!