Being able to see how long it took you to complete a full exercise. For example

5 sets of 5 reps of bench press completed in 2 mins and 22secs on March 11
5 sets of 5 reps of bench press completed in 2 mins on March 12


Also a progression calculator. if I want to benchpress 200 lbs by October JEFIT could calculate how much reps and weights I should lift per workout on a graph and I can use that to build my routine.