This small light-weight wireless call button will meet your requirement for wireless calling system.

It has three keys. Any customers need help, just press the key. 

There will be a screen or watch receiver to be used together.

Once the screen get the signal, it will broadcast, like "001 calling".

As for the watch receiver, it will vibrate and display "001 calling" or "001-01",

the first three numbers means the table number, the last two means the different custmoer service.

Then the waiter can provide service as soon as possible.