Just to clarify,
ANT+ consists of a collection of device profiles which ensure interoperability between devices of the same type, while ANT can be thought of as the wireless protocol itself.
The iPhone does not natively support ANT and you must use a dongle.
You do not need ANT+ to communicate with an ANT dongle unless you wish to send/receive data using an ANT+ Device Profile.
No hardware changes are necessary, but all ANT+ device profiles use the same network key and RF channel. The specific channel period, transmission type, etc are specific to each profile.
Cheers