What I know is when you receive Bitcoin you convert it to USDT or you leave it in Bitcoin and then trade it using P2P exchange, so if a supermarket is interested in accepting Bitcoin they should employ someone who will be in charge in doing the P2P trading, for now I don't think there's an auto-convert to naira app or device, however it can still be developed.
You don't need someone to do the conversion, there are payment processor that converts directly to NGN. Even if none is available, the processor can convert from Bitcoin to USD which is stable and less susceptible to fluctuation.
Ur wallets no be AI to detect wetin dey ur mind since exchange no even at all get that kind auto convert bitcoin to usdt feature.
Make u no also 1 day try am say u want u want use bitcoin network to send fund with any other usdt network believing say e go auto convert if not, u go dey risk to loose ur money.
Hmm... Haven't you heard about payment processor. Clearly, you didn't care to read the OP carefully.