You can view your iCal appointments alongside your SimplePractice sessions with the SimplePractice iPhone app. Download it here.
To see both these calendars together, go to the calendar in the iPhone app and rotate your phone sideways. In landscape view, you'll be able to see your full week with both SimplePractice sessions and iCal events appearing.
If your iCal events are not displaying in this landscape view:
1) Close SimplePractice
2) Open your iPhone's Settings.
3) Tap Privacy.
4) Tap Calendars.
5) You should see the SimplePractice app listed here. If the SimplePractice app is disabled in this menu, enable it now. If you don't see the SimplePractice app listed, try uninstalling the app and downloading it again.