Grandma Coin only works if both people want it to. This page is what the relative sees, what they are agreeing to, and how they stop.
One text message from a fixed Grandma Coin number. It names the person who added them and links to a page with no login. The page is one screen, large type, plain words.
"[Grandchild's name] added you on Grandma Coin, an app that gives you both a small piece of a stock every time you talk on the phone for 20 minutes. Tap to say yes and pick a stock. Reply STOP any time. No cost, nothing to install."
Reply STOP to any message, or tap withdraw on the consent page, which stays live at the original link. Calls stop paying immediately. Their wallet and any fragments in it are untouched and remain theirs. The grandchild is told the relative withdrew, without a reason.
Some relatives will be very old, and some will have someone helping them with their phone. If a caregiver taps yes on their behalf, the caregiver is confirming the relative understands they will get calls and a small holding in a stock they picked. We keep the consent page simple enough for that conversation to be a short one. If a relative seems confused about what they agreed to, the right move is to reply STOP and talk to them directly.
Relatives must be adults. Grandchildren must be adults too, because the app creates a wallet that holds a financial asset. A sixteen-year-old calling their grandmother is wonderful and should keep doing it, and should not need a stock to do it.