I saw a post on another board where someone was going through an old bike tool box and was finding a bunch of old stuff that was the rage at the time (early 90's or so). I also found something from the 90's that I thought still makes sense today, the Dirt Worm.
Specialized had an inner tube, that instead of a circle, was linear. You did not have to take off the wheel in order to put a Dirt Worm in. You just lifted one side of the tire bead, cut out the old tube, and thread the Worm in. The two ends would overlap. Re-set the bead, pump up the tube and go. At the time, taking a wheel of was not really a big deal with the QR, which is why I think they were not that popular.
However, now things have changed. You have axels, etc. All types of configurations where it is not really convenient to take off a wheel (on the trail). Enter the Dirt Worm. Heck, it would even work for the 69er bikes. Just sell the tubes as 29", you could still get them to work on a 26" wheel. They would only have to carry one tube, not two.
Results 1 to 3 of 3