Internally I had heard some info about Phi but wasn't really in the loop on it.
Phigolf is running a kickstarter for the device if anyone is interested. I think it explains everything pretty well.
It's a bluetooth device that allows the player to swing a real club and have that translate into WGT at a surprisingly low price considering what it costs for many similar experiences.
Players using Phigolf will not be competing in regular game modes, meaning you won't encounter them in coin games or in regular tournaments. They'll have tournaments set up specifically for Phigolf users and multiplayer will match them against another player using Phigolf.