I think that many people of the Christian perspective say that is against the bible to meditate, especially of the conservative evangelical type. I would say first yes your thoughts should be on God at all times and if you are focusing on your breath your attention is not on God. Alright that is a fair point. However, how many of these same evangelicals are fine with following there favorite sports team? Does God really care about your football team? I am mean you are so focused on your baseball team you are not focused on God. And I think that meditation and prayer can be used together. In the same meditation you could say at first be asking God for things and then thanking him, after you are all talked out you could just shutup and listen, and focus on your breath which would probably lead you to a state of pure silence which according to the ancient Vedas is the goal of meditation, ie to reach a state of pure silence. Okay you say well what about Vain repetitions to achive an altered state that is fundamental to the vedas. Alright then you don’t need to do a mantra how about just let your thoughts come and go and then you can perhaps reach a state of peace?
So I think that yes a Christian can practice meditation!