Is there a way to access the TOR network on iOS devices?
I suspect you would be able to use TorVPN's PPTP Server, just make sure you switch the "Send All Traffic" switch on the VPN configuration settings to "on". Otherwise it will be astoundingly ineffective :).

Note that I have not used this service, but knowing what iOS supports (L2TP/IPSec, PPTP, Cisco L2TP), I have a hunch that it will work.