True you do NOT need consent. You record anyone's convversation by phone or in a public establishment without the other party's consent. Now let's say if you had placed an audio microphone or video camera in that party's home, or motel room for an example...that is ILLEGAL! Straight from the moutj of a respected defense attorney I know.
In Iowa I'm pretty sure you don't need the other party's consent to record.
COVERTLY RECORDING TELEPHONE CONVERSATIONS