The Cell Phone was basically a successful attempt at replicating Kirk's flip communicator.
I know there is a lot of talk about the communicator/cellphone comparison. I don't see it (other than wireless devices used for communication). I always equated the communicator with walkie-talkies or military field radios. If you look at these items in the time period that TOS was flimed, you see that they required a person carrying a backpack full or radio equipment to allow communication with HQ, air support, etc. See Forrest Gump, Platton, or any other Vietnam era movie for an example.
Just my $0.02.