Portable buzzer/ alarm notification device

Would like to have a notification other then my Phone. A buzzer or quiet alarm that I can have on my person, like a key phob or something you can have sitting by you at the living room or bedroom, an something the size of the large side of the contact sensor. If an notification happens for children getting into to something or somewhere they shouldn’t. Or for a motion sensor detects someone coming up to the door. This alarm is more an informational then warning. Also for on the gate to the pool. Or closet where the Christmas gifts are keeper. PLEASE Vote. It could look like the motion sensor with a red dome with a flashing LED under it with the buzzer.