I searched Froogle for Cisco iPhones and found 2 models.  Both were
released in December 2006.

The following support webpage for the iPhone was published on Sept 12
2000.  http://www.cisco.com/warp/public/779/smbiz/iphone/

Linksys says the following in its Dec 18 release of the new iPhones:
"Since the summer of 2004, Linksys has shipped more than 3 million VoIP
products worldwide, including seven phones in its iPhone product line -
all immediately available in the United States:"

http://www.linksys.com/servlet/Satellite?c=L_News_C2&childpagename=US...

This news article from BetaNews the same day makes mention of the
acquisition of the trademark in 2000, but seems to indicate that Dec
2006 was the first Linksys use of the moniker "iPhone" for its VOIP
products: "Now, a "second re-introduction" has re-christened the CIT200
as the "iPhone Cordless Internet Telephony Kit," and the WIP300 as the
"iPhone Wireless-G IP Phone."
http://www.betanews.com/article/Linksys_iPhone_Announcement_Gets_Atte...

Besides, the USPTO has no mark "iPhone" for InfoGear.  It has
"IPHONENETWORKS."  Big enough difference?  Check it out for yourself:
http://assignments.uspto.gov/assignments/q?db=tm&sno=75501345

Furthermore, the USPTO lists the marks current status as "Abandoned: No
Statement of Use filed after Notice of Allowance was issued." as of
11-17-2000:
http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=75501345

So let's see, InfoGear files for and receives protection for
IPHONENETWORKS.  By Sep 2000, they have been bought by Cisco.  Two
months later the USPTO lists the mark as "abandoned."  In December
2006, Linksys releases an iPhone and claims that it is a continuation
of if 2 year old VOIP phone line.  But there is no record of iPhone
products prior to Dec 2006.

Yesterday happens.  Today happens.  What's tomorrow?

This didn't take but a few minutes of research.  The internet's a
wonderful thing.....