Bookamat - Powering the world's best independent fitness, Pilates and yoga studios.
Remind1 - Save nerves, time and money - send automated appointment reminder messages from the calendar you already use. Google Calendar & Outlook / Office 365 Integration.
appointman - Online booking solution for gyms and studios
Remindy.me - Never forget anything!
Glofox - Powerful Gym and Studio Management Software.
Appointment Reminder - Automated SMS/Voice and Email Reminders.