I have a NDA but yes, way back when we would pair to a device without any user input.
So yes it's possible but I find many engineers never wrote code at that level.
I will not be able to reveal more than this other than you can see such pairing in the open with that bluetooth to serial port device at serialio.com
I have signed a non disclosure for this so I can't say everything, but I wanted to know if this is possible. So there are two products that work together, and then bluetooth the info to an app on your phone. Product A will have an interface on it, but product B will not, nor will it have any touch sensitive method, it is very minimalistic and simple. Since B doesn't have input/interface, it would be harder to pair that with the phone. I was wondering if I could somehow pre-pair the two products so that when the user pairs with A, it would connect both of them together?

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