There are a number of questions on Mi Yodeya dealing with the halachos (laws) of walking in front of a Jew who is praying, for instance When you're trapped by someone Davening behind you
There is also a question dealing with walking in front of someone who is saying Kaddish. Walking in front of someone saying kaddish
Is there any notion of not walking in front of a Muslim who is praying? (An acquaintance made this claim but I have never heard of any source for anything like this.)