Something interesting I once saw on NatGeo: the anxiety that people experience in an allegedly haunted house is the result of infra sounds, coming from a source such as a nearby powerful engine. You will definitely have to check the sound spectrum ...

In Belgium we can buy parking time with a text msg. Just send aaaab licplate to an abbreviated number, and your parking costs get added to your cell phone bill. The guys that check have online access to the text database. aaaab is city-zone, licplate is just your license plate of course.

By the way, did you all know that sometimes there's more than one solution? Especially when the problem is wrong. Look at http://www.tspforum.com/sudoku.htm to see what I mean. In this case, the sixes and the fours are interchangeable. If the problem doesn't provide at least one of those four numbers, you're able to provide two solutions. It can even be a lot more complicated than that ...