"I am unclear -- can I use mindfulness and also be devout in my religious beliefs?"
Dear Unclear - Mindfulness is a way of "being" as a human. It's a way of being present to those we love, getting to know our deepest selves, and working with the messiness of this human existence. The being human part of mindfulness is about this plane of existence - how we use our human brains and our human form to be fully immersed in our lives rather than in our thoughts. In my mind, religious beliefs often support people to be more in touch with our "essence" qualities - or our holy selves.
I have the opinion that mindfulness can enhance religious beliefs and practices. We can bring awareness to the human choices we are making and look for guidance. If we are looking at mindfulness in a secular way, the guidance comes from within or from the collective consciousness and from many religions the guidance comes from some higher power. Gratitude is a huge part of mindfulness as well -- with many religions the gratitude is more focused to a specific higher power. Additionally, the loving kindness meditation has been likened to prayer. People have said mindfulness can allow us to get in touch with our "Buddha-like selves" or our "Christ-Consciousness" or however you view the most holy or true part of yourself.