I'm not aware of any device that does that. And I question the need. One beep would not be heard. How many beeps are needed? How long should it beep?
Really.
Why don't you create or have someone create an app for it?
The newer batteries and their current sensing firmware in the chargers actually stop charging when the battery is full.
Hey, can I ask a really obvious question I've never had a good answer to?
Why the heck doesn't iOS signal with a beap or other manner that your iphone is fully charged and you can now unplug it? I had two very excellent flip phones prior to my iphone and they both had several options to notify me that they were now charged.
I still believe the batteries perform best if one unplugs the charging chord after a full charge is achieved.
But, does anyone know why the iphones don't seem to have this very basic capability?

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