Predatory towing companies being in the news at the moment... and still being a thing after all these years... I find inspiration striking.
Once your car has been removed from its parking space, it's just your word against the towing company's as to where it was parked... and any accusation of Grand Theft Auto on your part will be cheerfully ignored by the Authorities so long as the pirates have kept up on their Thieves Guild dues.
Ergo, a standby-mode black box. A datalogger that keeps operating for a few days (not forever; don't want to drain the battery) after the car is parked. Records GPS data (there's a module out now that claims 1.4m accuracy), motion (3-axis accelerometer), and engine on/off status.
So, in the event of your car being towed, the hidden black box records exactly where it was parked, when it was taken, and where it was taken. Evidence!
And, even with the high-res GPS, this dingus could sell for quite a bit less than a towing charge (though installation, if not DIY, might run a fair bit more). Isn't it worth it, for the chance to send a scuzzball to prison?
For those with a bigger budget, add a cellular data modem and send the data To The Cloud. That way, you don't have to retrieve your car to retrieve the location data (and this works even if it's been stolen by unlicensed thieves). But surely this is already a product, right?
Hm. Assume it stores, oh, 64 bytes/sec on average when in motion, and much less when stationary. A modest 8Mbyte flash chip would hold 36 hours worth of while-moving data. A 64Gbyte SD card would hold enough for 33 years in motion. I'm thinking either a largish SPI NOR flash part, or a small eMMC.