All the torque sensing diffs are a major improvement over the positraction style diffs. There are a number of good torque sensing diffs available, several have already been mentioned. There is only one that comes with a transferrable limited lifetime warranty no matter if used as a daily driver or as a diff in a high powered race car on a race track or both and it doesn't matter where you break it (If you can), it is warrantied — for life.
The company that offers it is Wavetrac and the diff has the same name. It also has some very nice torque biasing design differences that work exceptionally well and not surprisingly, they patented them. Here is a link to their site =>
Wavetrac . Check out the how it works video on the technical tab.
Ed