A method comprising: receiving, by a mobile device , a first location request requesting a location of the mobile device , the first location request specifying a requested accuracy threshold, wherein the mobile device is a wearable computing device; determining, by a location determination subsystem of the mobile device, a first location estimate of the mobile device , the first location estimate being associated with an uncertainty value that is determined by the location determination subsystem ; determining whether the uncertainty value satisfies the requested accuracy threshold; in response to determining that the uncertainty value does not satisfy the requested accuracy threshold, determining, by the mobile device , that the location determination subsystem of the mobile device is incapable of determining the location of the mobile device at the requested accuracy threshold under current conditions; in response to determining that the location determination subsystem of the mobile device is incapable of determining the location of the mobile device at the requested accuracy threshold, establishing a wireless communication channel between the mobile device and a companion device using a protocol in which a communication range between the devices is less than the requested accuracy threshold and submitting, over the wireless communication channel, a second location request by the mobile device to the companion device that has paired with the mobile device ; and in response to receiving a response to the second location request from the companion device , the response including the location assistance information, determining a second location estimate of the mobile device based on the location assistance information, and submitting the second location estimate corresponding to the location assistance information as a response to the first location request. receiving, by a mobile device , a first location request requesting a location of the mobile device , the first location request specifying a requested accuracy threshold, wherein the mobile device is a wearable computing device; determining, by a location determination subsystem of the mobile device, a first location estimate of the mobile device , the first location estimate being associated with an uncertainty value that is determined by the location determination subsystem ; determining whether the uncertainty value satisfies the requested accuracy threshold; in response to determining that the uncertainty value does not satisfy the requested accuracy threshold, determining, by the mobile device , that the location determination subsystem of the mobile device is incapable of determining the location of the mobile device at the requested accuracy threshold under current conditions; in response to determining that the location determination subsystem of the mobile device is incapable of determining the location of the mobile device at the requested accuracy threshold, establishing a wireless communication channel between the mobile device and a companion device using a protocol in which a communication range between the devices is less than the requested accuracy threshold and submitting, over the wireless communication channel, a second location request by the mobile device to the companion device that has paired with the mobile device ; and in response to receiving a response to the second location request from the companion device , the response including the location assistance information, determining a second location estimate of the mobile device based on the location assistance information, and submitting the second location estimate corresponding to the location assistance information as a response to the first location request. <EOS>