The FCC has not approved the iPhone; it is a watchdog agency mandated to ensure compliance. The manufacturer is responsible for complying with the law. Apple is out of compliance and thus the coming complaints to the FCC.
Below is an excerpt taken from the website:
http://www.fcc.gov/cgb/consumerfacts/accessiblewireless.html
For manufacturers of digital wireless handsets for use or imported for use in the United States:
• By September 16, 2005, each such manufacturer had to offer to service providers at least two ANSI U3 or M3-rated hearing aid-compatible handset models for each air interface offered.
• By September 18, 2006, each manufacturer must offer to service providers at least two ANSI U3T or M3T-rated hearing aid-compatible handset models for each air interface offered.
For both digital wireless service providers and manufacturers:
By February 18, 2008, fifty percent of all handsets must meet the ANSI U3 or M3 hearing aid-compatibility requirement for each air interface offered.
For additional information about the FCC's actions with regard to hearing aid-compatible wireless phones and other steps the Commission has taken to ensure that individuals with disabilities have access to telecommunications services, please go to www.fcc.gov/cgb/dro. You may also contact the FCC's Consumer Call Center at 1-888-CALL-FCC (1-888-225-5322) voice or 1-888-TELL-FCC (1-888-835-5322) TTY