"Maha-Stamaprapta Bodhisattva's Preachment on Being Mindful of the Buddha" (大勢至菩薩念佛圓通章) is a part of the Shurangama Sutra. Here's a complete video with the text which is read by Venerable Hui Ping (慧平法師). You can see the animated cartoon video describing this on my previous blog post.