I have a TT4. It does what it says. I forget if I have the kit one or not, but I also have a little LCD display that I can tinker with. Where there any questions specifically you have about it? I run a Garmin GPS 18x LVC puck with it. I used it with a FT-8800, so I built a 8-pin DIN plug harness to use with it, pigbacked power from the radio itself. You'd have to built a mic & speaker interface for your FT-2900, but it would work fine.
"Why does the U.S. care which flag will be hoisted on a small piece of land thousands of miles away?" -- Ron Paul