Ability to send invoice/manual sale from mobile app
I have to go to my computer to invoice a client for a sale for them to pay. It'd be easier if this can be done on the phone.
Marlon Goodchild commented
Make a way for clients to pay trainers directly through the app. Send reminders when payments are due.
Have a paypall hookup in the app where your clients can pay you if their on a subcription plan