I use this with my Anatomy class, but it would work well with any other class in which you discuss reflexes.
The first part requires students to have a partner; one person drops a ruler and the second person has to catch it. Students use the provided equation to change the distance at which they caught the ruler into the time of their reflex.
The second part requires a computer and is divided into two sections. Section 1 uses a really fun site from BBC in which students have to tranquilize sheep. My students LOVE this site and have a ton of fun with it.
Section 2 has students research reflexes common in infants. The list of reflexes is provided, but students have to do some digging in order to answer the questions.
This takes my efficient students one class period (40ish minutes). I assign the leftovers as homework.