The BluAlert vibrating wristband is no doubt superfluous for most occasions, but might serve a purpose at ridiculously loud events. The device wirelessly connects via Bluetooth to your cell phone. When your phone rings or receives a text message the wristband vibrates. Once paired, the BlueAlert wristband also includes a 15’ proximity alarm in the event that your cell phone decides to take a walk. 3 hour charge time and 100 hour standby time.
Available here for $63.