Hey STik, here's the CG-Lock site:
http://www.cg-lock.com/index.html.
They're metal devices that clamp to the seatbelt tongue and let you snug down the lap part of the seatbelt while leaving the shoulder part free to move with you. Basically, it makes the lap belt portion of your seatbelt work like the seatbelt on a plane. But, you can loosen it without unlatching the seatbelt if you want to also.
I really like them! They really keep your butt in the seat, whether bouncing around offroad or in a tight turn in a fast car. I've been using them for 4 or 5 years now, and I've installed them in multiple vehicles for myself and my family. Personally, I feel like they make you alot safer as well, as if you're using it, your lap belt is already snug and in the correct position in the unfortunate event you're involved in an accident.
You can slide off the the top plate (don't recall what the company calls this piece) of the device and it returns the seatbelt to normal functioning without having to remove the device from the seatbelt.
Just an FYI - On every install I have done, I had to use a Dremel with a sanding drum on it to shape the tongue of the seatbelt somewhat and add some texture so the CG-Lock would mount up and grip properly. Something I found out by trial and error. But, with doing that and Loctite-ing the screws, I've never had one come loose.
Not for everyone maybe, but I won't own another vehicle without putting one at least on the driver's side for me to use.