The other good thing about Option#2 is that visitors do not have to give you their mobile phone number (which they are doing by sending the text).
Just because they are at your door for some reason does not mean they want to give up what has become their mobile ID. People are starting to get protective of it with good reason, since there are so many attacks using the Mobile #/ID...
Also, as pointed out elsewhere, the static easily duplicated QR code has issues for you, but it would also be easy for someone to slap a malicious QR code over your static one, disabling yours and enabling their scam...
Maybe I'm just the wrong generation, or live in a place that still has winter, but a QR code where I need to get out my phone, take off my glove in winter, activate the camera to scan, etc., seems a lot less welcoming.
One thing that is good about your QR code option is that you do receive notice anywhere and you do have their mobile number, so you can reply immediately with a text or call, such as "sorry, I'm running late, not quite home yet, I'll be there in 10min". Ofc, you could also post your mobile number below the wireless doorbell.
Perhaps Option #3 would be a doorbell that can display a scrolling message, so
— wireless doorbell
— sends text to you
— you can reply to doorbell (e.g., "coming downstairs now", or "traffic, be there in 5min", "pls call me at 987-654-3210", etc.)
This way, no one needs to reveal their mobile number, but everyone has the advantage of mobile communications, albeit with a small bandwidth.
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