Imagine a gadget that fits in your back pocket and lets you surf the Web anywhere, write documents, make VoIP calls, watch movies, and listen to your entire music library. That´s not exactly what Nokia had in mind when it released the 770 ($360; nokia.com), a PDA-size Internet tablet with Wi-Fi and Bluetooth. But because the device has an open-source operating system, anyone can build new programs for it, endowing it with nearly endless functions (we´ve nicknamed it the HackBerry).

For a closer look at how the Hawk-Eye works, launch the photo gallery by clicking 'View Photos' at left.

Its accuracy may be based on a complex computer-generated algorithm, but the Hawk-Eye Tennis Officiating System is ratcheting up the human drama at this year's U.S. Open. Rather than simply relying on officials to make line calls, the entire crowd now acts as referee, hollering "Challenge!" after controversial judgements.