This looks like an attempt to overcome Motorola's patent which is in place for many years, at least on the phones sold in Canada. Motorolas have a tiny patch of white compound which turns red or black after contact with water. I have a couple of those at home with voided warranty like that.

It is some kind of improvement comparing the not so reliable indicator sticker which is used on almost every phone (including Motorola) behind the battery. If I understand your comment well, you're talking about this sticker. Apple introduced an improved solution.

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