By the end of this year, Wherify Wireless Inc. hopes to market a playful-looking child’s watch. Even though it tells time, its real purpose is to provide the whereabouts of the wearer 24 hours a day by using global positioning satellite, or GPS, technology. The first generation of the personal locator, which packs an impressive amount of technology into a 3-ounce package, seems a tad out of proportion on a small child’s wrist. It functions as pager, features a 911 button for emergencies, is cut-resistant and can be locked in place. In less than a minute, a parent can pinpoint the whereabouts of a child within a few feet by logging onto the Web or calling a Wherify operator. Wherify plans to sell the device to consumers for between $300 and $400. Depending on the level of service selected, the company will charge between $15 and $30 a month. The company expects not only to market the products to parents fearful of child abductors and molesters, but also to the adult children of Alzheimer’s patients and anyone else who may want to track the location of someone. The device is the first of hundreds the company wants to sell that will use its service platform. Similarly, San Francisco-based Televoke Inc. is working with a growing list of partners to develop products for its competing location-based services platform.