If we're talking about license plate numbers, it seems fairly reasonable to just have the device download the entire target list.

Longest plates are 8 chars. It seems exceedingly unlikely that the target list is longer than 1,000,000 plates. They all use characters that fit in a single UTF-8 code point. So 8mb initial download, and very small incremental updates.

Likely much more power efficient than sending every plate over the network, and would use considerably less bandwidth over a couple months.

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Is that how they do it? No freaking clue.

But it seems like a very solvable problem, with correctly aligned incentives (ex - it's both cheaper and more private to NOT send the plate over the net, vs sending the list to the device).