Brian - do you guys push your appointments to a central calendar like Google Calendar, Redtail, or does your calendar system have iCal abilities?
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I have a lot of experience using these guys and they utilize shortcodes. They offer both SMS and email confirmations. You would probably need a custom plan, which they can tailor to your needs, but they've been very reliable and support is great. There are workflows and such you can set up with the system to send them to a confirmation link and you could specify technician photos on the confirmation link/page based on various parameters that you set in the workflow such as the calendar name. They can support more than 25 calendars as well and I think they'd come way under the $1000 / month price that Fred mentioned. Your office staff can log in and chat back and forth with the client if needed too.