This is really clever and well done. Like someone else below mentioned, I love how the interruptions feel really inconvenient. It gives a nice reflection of the experience of the character. I also thought the gameplay of the marking, while simple, was nice, and absorbing enough to make those interruptions seem noteworthy.
My only complaint is with the typing; maybe this was on purpose, but not being able to see what I need to type more than one word ahead somehow ended up being kind of annoying and difficult. Perhaps my brain just can't work in such little chunks at a time.