Kept on this device only and never sent anywhere. There are no notifications and never will be — if you want a reminder, set a repeating calendar alert for the first Friday of the month.
Communion on the first Friday of nine consecutive months, offered in reparation to the Sacred Heart. Nine months, not nine days — which is the whole difficulty and most of the point.
The devotion comes from the revelations to St. Margaret Mary Alacoque, a Visitandine nun at Paray-le-Monial, in the 1670s. Attached to it is what is usually called the Great Promise: that those who receive Communion on nine consecutive first Fridays will be given the grace of final repentance — that they will not die without the sacraments, or outside God's friendship.
That promise is private revelation. It is not doctrine, and no Catholic is obliged to believe it. We describe it rather than quoting it, because the English versions in circulation differ from one another and none of them is a transcript.
It also is not a mechanism. Read as a guarantee that nine Fridays purchase a safe death regardless of how the intervening years are spent, it becomes exactly the vending-machine religion this site refuses everywhere else — and it would make no sense on its own terms, since what is promised is the grace of repentance, which is something a person still has to accept. If the promise is doing any work at all, it is working on people who keep turning back.
Pray it because reparation is worth making. If the promise is true, it is a gift and not a purchase.
Read this before you begin. Reparation is a love response, not a debt you are servicing. Nothing is short. Nothing is owed. You cannot make up a deficit on Christ's behalf, because there is no deficit.
Which means: if this practice starts producing anxiety about whether you have done it correctly, or whether a missed month has cost you something, put it down. That is not permission to be lax; it is what the devotion actually is. A count kept out of fear is not reparation, and the Heart it is offered to is not keeping score.
The same goes in the other direction. This is not evidence that you are a more serious Catholic than the people at your parish who have never heard of it. Most of them have not been told. That is a failure of catechesis and not a fact about them.