BackTone 4000 Posture Training Device - Large Worn like a backpack over clothing, this lightweight posture training product can help teach correct spinal alignment. Every time you slouch, the shoulder straps of BackTone pull on the device and sound a buzzer or cause the unit to vibrate. The only way to stop the sound is to straighten up. Wear BackTone for 20 minute training sessions daily. ou can also choose a short vibration option for use in situations where noise is an issue. The BackTone can be used sitting, standing, or walking. Continue with your activity, straightening up every time BackTone beeps or vibrates. Your body quickly becomes accustomed to using correct posture.