The Wherifone is not, however, a fullblown cellphone. It looks and acts more like a Star Trek communicator. Its screen is crude, tiny and black-and-white. There’s no Internet, ring tone downloads, games, camera or text messaging, though some parents might consider that a bonus. The phone has a hissy quality that makes all calls sound as if they’re coming from the seashore.

The phone from Guardian Angel Technology (guardianangeltech.com) is quite a collaboration; the company makes neither the phone (Motorola), the cellular network (Nextel), nor even the billing plan (Boost Mobile).

Instead, what this company brings to the table is the GPS software. The company offers three phone models, none of them cutting edge, and one of them (the $75 base model) looks as if it’s from 1994. You can also buy any phone from the greater selection at boostmobile.com, and send it to Guardian Angel for GPS enhancement. Many of these phones offer Nextel’s walkie talkie feature.

On the upside, the GPS tracking on the Guardian Angel phones is more sophisticated than its rivals’. For example, you can see a full 30 days’ worth of “bread crumbs,” which could settle the occasional argument about your teenager’s whereabouts the last few weekends. And you can opt to have street names superimposed on the satellite photo view (just as in Google Maps, which powers this feature).

The downside is the pricing: $30 a month just for the tracking. You can start and stop this service as needed, but it’s still much more expensive than its rivals.