One of Mary's great gifts to her children is the Green Scapular. It was given by Our Lady to Sister Justine Bisqueyburu, a Daughter of Charity of St. Vincent de Paul, in 1840 (just 10 years after St. Catherine Laboure, in the same order of nuns, received the Miraculous Medal).
It's purpose: Cures and Conversions. The only prayer to be said is the inscription surrounding the heart: "Immaculate Heart of Mary, pray for us now and at the hour of our death." These can be given to the person being prayed for, or, should they resist, can even be tucked away in an inconspicuous spot in their bedroom or home. The important requirement is that you pray for them with great confidence. This devotion was twice approved by Blessed Pope Pius IX.
They are available singly or in packs of 20. A flier describing the requirements of the Green Scapular is included. Picture shows front and back of the Green Scapular.