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.
'91 Pickup - Imelda
'08 Tacoma TRD
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29
"To live is to suffer, to survive is to find some meaning in the suffering." -- Friedrich Nietzsche