I used my hand-written notes in 9th grade last year, and they worked wonders, especially when kids would get a note thanking them for their choice. This year, it'll be for 7th and 8th graders.
There's another one on Pinterest in a similar vein--it said, "Stop what you are doing! Re-think your behavior choice. Bring this card back to me when I'm not busy and tell me what you were doing wrong, and how you are going to make better choices."
I like the idea behind it--I think it's a little harshly worded, so I'd change that a bit, but it's interesting.
Definitely adding: "thanks for speaking up in class today!"
"I'd like to hear from you today... prepare an answer for the next question, which will be _______________________." If I laminate them, I can write in expo marker what today's questions will be. =)
I'm trying to think of a way to prompt students to work in a way that is productive--maybe something along the lines of, "You can either begin working diligently, or step outside and talk to me about why you aren't. Your choice--sitting and staring is not an option."