Ian Hickson came up with Hixie's Natural Log in September to use the checksum idea to use the last two digits for a review of the restaurant, the quality of the drinks, was a vegetarian selection available, was wifi available, and how many guests ate at the meal.

We can set any number from 0 to 99. In binary, that's 0b0000000 to 0b1100011. In other words, we have seven bits to play with, except that if both of the high bits are set, then we lose bits 3, 4, and 5. [Source]

Of course, it failed because of the inconsistency of the waiters and restaurants to bill what he wrote down. See the Hixie's Natural Log explained.