And what problem is there with sticking the key card in your wallet? Works for me, every time, cell signal or not. If the phone doesn't respond AS I WALK UP, I have my wallet against the B pillar, and viola, it unlocks. I can't believe some people insist on waiting while their wife brings a "key", whatever that is, because the key card is "too big" to carry in a wallet right behind the required Driver's License, etc.
Don't ever rely 100% on only one way to do much of anything electrical. If your Ring button doesn't work, put a sign, "Please Knock".
By the way, the phone works flawlessly, most of the time.