IP.Board has their own iPhone app, but apparently the version Groundspeak is currently using is not supported. Got this from them the other day:
Invision Power Services
Security Update: 27th December 2012
A critical security issue has been reported to us, and we are releasing a critical security update today to patch this issue.
Instructions
We are providing a patch for IP.Board versions 3.4, 3.3, 3.2, and 3.1. Version 3.1 is end of life for support but we are still providing the patch for the convenience of clients who have not yet upgraded. If you are running a version less than 3.1 you should upgrade to get this and other security enhancements.
Please read the announcement for complete details.
Invision Power Services · Unsubscribe
This may just be revenue generation, but maybe it will encourage them to upgrade.