So here you can include a bunch of things that are client specific. You can have a welcome message, You can have a pic of them like the really tired guy to the left here who hates his kettle bells. You can also have it post random motivational quotes.
They can check their schedule with you. They can pay invoices. You can upload their workouts so they can see how they'be been doing, take progress pics so they can check out those, pretty much anything you think might be cool to keep clients. You can post messages for them here too. People lose emails but if you post message or documents in one central place for them they can always find them instead of hunting through their phone or computer. I dont know if you ever need or want to do that, but ya know, you could.
So, buttons. The buttons are all conditional, if you have a message, the button tells you how many, if you owe on an invoice, the payment button shows up, otherwise it disappears. The only button that actually functions here is the schedule one though.