QuoteBoost Mobile, a so-called mobile virtual network operator owned by Sprint Nextel, will offer a two-hour demonstration of buddy-tracking technology created by a start-up called Loopt. The start-up, founded by two Stanford University graduates while they were still students, is the latest to offer a mobile tracking system that allows people to do things like get a bead on friends' whereabouts. It certainly won't be the last. For nearly a decade, technology visionaries have talked of a day when people would be able to use their cell phones to get directions, track their friends, keep tabs on their kids or simply find the nearest coffee shop. Now those services are finally starting to take trickle into the marketplace.