As far as I know the software for the "probe" is already in Mach 3.
Any "metal" object is placed on the table, and the tool moved to it. When the tool touches it, it stops. (The metal object must be electrically isolated from the table ) A wire is connected to the metal object and fed into LPT1 input pins and the Config/Inputs/Probe is configured as the input, "active low". If you notice a clip was put on the tool to help with earthing the "target" when touched, but apparently this is not always required.
There is a similar post submitted by Benny further down the main page "Check out this post"
This appears to be a very useful tool - can anyone tell us if this is in Mach3 - and what the syntax is