Mine is labour intensive and low tech. I lay my quilt full out on the floor. I use my large 15 inch square in a corner and line up all my rotary rulers up to the next corner. I slide my rotary cutting mat under the edge and trim, moving the mat as I go.
I like the idea of the laser light for squaring up but so far can't justify the cost and I would still need to move the mat and ruler to trim.