1. Do you attend any fitness classes?
I am a competitive powerlifter. I have a trainer I meet with one-on-one 3x a week and attend one class on saturdays that he hosts. Class is free and open to all gym members, but isn't well attended. I go in the hopes that other members see people in the class and join. I'm more there to support my trainer than anything else.
2. Would you use an app like this to see all fitness classes in the area?
Every gym in my area is closed to non-members. For this reason I would only attend classes at my home gym. My gym offers an iCal integration with their master schedule, so the app you are suggesting would be redundant for me.