I have been using the "ticket in" approach to check comprehension & preparedness (as well as take attendance) for several years. Students know they will be held accountable for completing the at-home readings with their ticket in. Additionally, students can ask question that they had about the readings for me to address in class on their ticket-in. It has proven to be a low stakes, high efficiency assessment of readiness to learn, as well as clarifying information they encounter between class sessions.
This semester, I intend to add a "ticket-out" assessment, where the student reports (on the back of the same index card as the ticket-in) the most interesting thing they learned in class and why; as well as has an opportunity to ask questions which I will address in the next class.
Student feedback on the ticket-in has been excellent. I will investigate through student response if the ticket-out has added value by increasing attention in class, forcing a review of class content, or getting their questions answered more quickly than without the second assessment.