A mobile app for the gym would be nice. It looks like you're only charting the number of reps. What about weight and time spent per exercise? Caloric intake?
I decided to keep the app as simple as possible, 6 months from now looking back at your stats - reps and time spent really wont matter (i.e. if you're tracking your 5 rep max then, and your 5 rep max now, time spent wouldnt really change).
There is a lot of competition out there - specifically in the mobile space, and certainly in the caloric space. I'd rather underdo them all and focus on a bodybuilder's needs for now.
Thanks for the comments! :)