Bluetooth Distance Approximations: Another idea is to perform Bluetooth dis- tance approximations. These can be rough, as one example application can be to adjust a phone’s ringtone depending on the proximity to the user. When the user is close to the phone the ringtone volume is reduced, and when the user is far away the ringtone volume is increased. Another example application is automatically pairing the phone to a pair of Bluetooth headphones or a hands-free device when the device is within a set distance of the phone.