Bad call reception at home? A new mobile service allows you to seamlessly place calls on both your cellular network and on any open Wi-Fi hotspot

Cellphones, which are supposed to let you call from anywhere, often work worst in your own home; signals can´t penetrate walls as well as they travel urban canyons and the great outdoors. But T-Mobile is hoping to change that, rolling out a service today that allows users to hop on their home Wi-Fi network or any other hotspot to make calls when cell signals are weak.

Today’s Global Positioning System is great for tracking tanks in the desert, but turn on your Garmin in New York City or inside virtually any building, and you’ll be staring at satellite static—GPS doesn’t perform well indoors or in urban canyons. Now a new technology is poised to pick up where GPS satellite signals cut out.

Developed by Rosum Corporation in Redwood City, California, TV-GPS, as the system is known, triangulates positions using television signals that are 2,000 times as strong as GPS satellite transmissions.