“We believe that Christian movies are the greatest evangelical tool of our time,” director David Nixon told an invited audience at a Feb. 22 preview screening of “Letters to God”

A sometimes moving, sometimes awkward blend of sentimental family drama, childhood cancer education and Christian proselytizing, “Letters to God” is the latest feature film targeted at the niche moviegoing audience that turned 2008’s “Fireproof” with Kirk Cameron into a surprise $33 million box-office hit. (“The Grace Card,” shot in Memphis last year with financing from Cordova’s Calvary Church of the Nazarene, hopes to be one of the next.)

“Letters to God” was co-directed and co-scripted by Nashville’s Patrick Doughtie, who was inspired by his young son’s fatal struggle with cancer. The movie casts Tanner Maguire as Tyler Doherty (instead of Doughtie), an 8-year-old boy whose brave cancer battle is a source of inspiration but also tension in his loving, close-knit family. “I just wish everyone would stop quoting the Bible to me,” says Tyler’s attractive widowed mom (Robyn Lively), in one of the movie’s more realistic moments. “It’s not curing my son.”

Embracing the Almighty as a sort of heavenly pen pal, Tyler begins composing and mailing daily prayer letters that are addressed, simply, to God. (“It’s not lame, it’s like texting your best friend,” he reassures naysayers.) In a typical missive, the plucky youngster asks: “Why am I sick, God? The medicine stinks, but I don’t have to take my spelling test this week, so that’s good.” He also writes: “I really wish my mom would laugh. I miss that the most… Dear God, please find someone for my mom.”

Cue the mailman: Tyler’s letters are intercepted by a substitute postal carrier in need of redemption, a divorced alcoholic Iraq War vet (Jeffrey S.S. Johnson) who might see the light sooner if only he could hear the lyrics of the country song that accompanies him on the soundtrack when he makes his rounds of the local bars: “There’s no message in this bottle…”

Author John Beifuss is the movie critic for the Memphis Commercial Appeal