Teacher's pets invent cellphone detector, get beaten up after school

Some enterprising New Zealand schoolchildren have developed a cheap (about US$48) cellphone detector which they say is for use in deterring classroom texting, exam cheating, and unauthorised cellphone use in a variety of other environments (plane cabins, prisons, and so forth). We bet they're really popular with their classmates now. At least they're not out rustling sheep or something.