You can export the calendar that you have in Wealthbox to your iPhone's calendar in a read-only format.
To do so, go into your Wealthbox account > Applications > iCal > "Settings". Here you will find a link which you may copy and paste into your iPhone. Click here to find your calendar web address.
On your iPhone:
1. Go to Settings > Passwords & Accounts
2. Choose "Add Account"
3. Select "Other"
4. Under Calendars, choose "Add Subscribed Calendar"
5. Paste the .ics address from the Wealthbox calendar into "Server"