The Collaborative International Dictionary of English v.0.48:

Prayerful \Prayer"ful\, a.
   Given to prayer; praying much or often; devotional. "The
   prayerful man." --J. S. Blackie. -- Prayer"ful*ly, adv. --
   Prayer"ful*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prayerful
    adj 1: disposed to pray or appearing to pray

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "prayerful":
   Christian, Christianlike, Christianly, adorant, adoring, begging,
   believing, cadging, cultish, cultist, cultistic, devoted,
   devotional, devout, dutiful, faithful, godly, holy, imploring,
   in the dust, mendicant, mooching, on bended knee, petitionary,
   pietistic, pious, precative, precatory, prostrate before,
   religious, reverent, reverential, scrounging, solemn, suppliant,
   supplicant, supplicating, supplicatory, theistic, venerational,
   venerative, worshipful, worshiping