apparently you can, but it depends on whether your car manufacturer provides an app to do it.
https://www.directcarbuying.com/blog/can-a-smartphone-be-used-as-a-car-key
2007 Honda Fit $4,400
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Yard Sale - Lots of great things! Sale Date: Jun 1, 2024
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… use a smart phone as a keyless remote for a car?
Thanks