I like Snapz Pro X for the Mac,
by Ambrosia Software.
I do Photoshop, InDesign, and Final Cut tutorials for my students
and this little program has never let me down.
I haven't tried it in the newer versions of A:M,
just with 10.5 -. It had a problem that caused the
slider tab near the frame indication area
to duplicate itself everytime it was touched.
It worked great on any other part of A:M though.
I'll have to check it on the newer A:Ms
and get back to you.
Edit: Just checked it with 11.1i and it works without a hitch.