1. I used to have (past tense) a ruler that had the rotary cutter attached to it. I think it was made by Fiskars, but I'm not 100% sure. In theory, it was an awesome idea, but in reality, it was a pain in the patootie. The stoppers on the ends kept coming off, which would allow the rotary cutter mechanism to come off the ruler. You had to really pay attention not to push the mechanism right off the end of the ruler. Eventually both stoppers got lost, and after that, the cutting mechanism fell off and got lost as well. Even before the ruler fell apart, the table under your cutting mat had to be 100% PERFECTLY smooth and level, or the cutter would miss whole sections of the fabric. It was easier just to use a regular ruler and rotary cutter.
2. My DH bought me a set of June Tailor rulers one year for Christmas. If I remember correctly, there was a 4-1/2", a 6-1/2", a 9-1/2", and a 12-1/2" ruler in the set. The problem was that the rulers have a 1/4" border (seam allowance) around them, and the measurements start AFTER the 1/4". It's very confusing to cut specific-size fabric pieces, because you have to subtract the 1/4" to get the size you really want. They're made of a flimsier material than Omnigrid rulers are, and several times I've taken slivers out of the edges of them with my rotary cutter.