Currently there is a switch at the top of the stairway which controls lights at the top and bottom of the stairs. However, it is not a 3 way switch (only controllable from upstairs). Also, it's run with 14-2 wire, so there's really no way for me to change it into one (the wire run would be almost impossible to change to 14-3 without some major deconstruction).
Just wondering if a wireless 3 way switch installed in the basement to control those lights will meet code?
Since they are on the market and that they are covered in "Wiring Simplifed" 42nd edition based on the 2008 NEC, I'd say they are permissible. The switch that is connected directly to the structure wiring would be the piece that would be affected by the NEC the most. It will be L&L for this purpose.