Don't know what your thoughts are on this, but I had a few customers that thought this was brilliant. Since putting them in no one has bought them (although saying they are a good idea). So all I have is good feedback from before we got them into stock.
Impact PipePower - Conduit Pipe Threader for your Impact Driver - http://www.impactpipepower.com/services/pipe-power-impact/#track-drill
Impact PipePower - Conduit Pipe Threader for your Impact Driver - http://www.impactpipepower.com/services/pipe-power-impact/#track-drill