The BT-821 is a high performance, Bluetooth GPS receiver that is WAAS/EGNOS enabled by default and incorporates the 20-channel SiRF III GPS chipset. Combining the BT-821's Bluetooth wireless technology with a Bluetooth enabled devices such as Smartphones, PDA's or laptops which support Serial Port Protocol SPP (regardless of their operating system) and your favorite navigation software (street, topo, ocean, aviation), you can create a sophisticated navigation system at a fraction of the cost of larger dedicated navigation units. The BT-821 offers up to 23 hours of continuous use from a single charge, making it the ideal GPS for extended navigation trips, whether on the road or on the trail. Battery usage is substantially decreased by having a built-in auto shut-off feature that power's off the BT-821 after 10-minutes of no active connectivity with the host device. Should the BT-821 ever be accidentally left on when exiting a vehicle, or within a backpack, the auto shut-off feature will power-off the GPS receiver to conserve battery resources.