If you need an app to pray . . .

. . . I will say a prayer for you.

You don't even need the 'closet' referred to at Matt 6:6:

But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly." (KJV)

Tu autem cum oraveris, intra in cubiculum tuum, et clauso ostio, ora Patrem tuum in abscondito: et Pater tuus, qui videt in abscondito, reddet tibi. (Biblia Vulgata)

Related words: closet, claustra, enclosure, claustrophobia, exclaustration.