I wouldn't say that.
My personal experience is that the noun in the phrase "just a _ away" is necessarily based on a verb.
If you need to text to activate the bike you could say "Just a text away!"
If you need to call to activate the bike you could say "Just a phone call away!"
If you need to tap an NFC chip to activate the bike you could say "Just a tap away!"
The point here for me is that the noun in this phrase is directly based off of a verb infinitive. You can't use any noun.
I agree. The standard advertising phrase is "is just a <quick action> away". That means "in the time it takes to do this quick action, you can have the thing you want". The whole point of the "just" phrase is "you can get this quickly". It answers the question "How far away (in time) is this thing that I want?"
I don't know what "is just an <object> away" means, but it does not mean "just a short time away".
Thank you very much for letting me know that “rule”. The way to activate a shared bike is to scan its QR code with a mobile phone to unlock the bike. So can I say “access to shared bikes is just a scan away”?
Yes, that sounds good. It is a clever way to say "access takes only a few seconds", which is valuable info.
Note: China is way ahead of the US, in the area of "paying for things by scanning a QR code". I think it is still uncommon in the US, but (based on what I've seen in videos online) it is very common in China.