I know Tejas pits use a knock-off version of the Blu-Flame log lighter system. It's basically a tube with holes drill along the length of it and works decent enough. Go to their website for more detailed pics.
Many others (Gator, ETSC, etc.) use a fish fryer type burner welded into the side of the firebox at grate height. I have this type and am very happy with it. The addition of an electronic igniter really makes it handy.
Common sense rules with gas-assist. Leave the firebox door open and the exhaust open at all times it's fired up. Do not leave unattended and you're good to go.