I've seen a few systems that have added a MPG (manual pulse generator), but they were all over $100 and usually still wired to the system. I wanted something less expensive AND wireless. So instead of an MPG I used a relatively inexpensive (around $30) logitech wireless number pad. I use it manually jog the machine when I'm away from the computer. I used a piece of software called AutoHotkey to map keys on the keypad to shortcuts in Mach3. So I can move all 4 axes, turn on the spindle, and run the auto-zero macro. It's not as precise as an MPG, but it gets the job done. I've been thinking about adding some shortcuts to change the jog speed so that I can make it a bit more precise.