Budding yeast monitor shape and the assembly of cytoskeletal structures and convey this information to regulators of cell division, but the molecular mechanisms responsible for monitoring and interpreting spatial information about the cytoskeleton remain poorly understood. A paper in the September issue of Molecular Cell shows that direct binding of components of the septin cytoskeleton may relieve autoinhibition of a conserved checkpoint kinase, creating a simple molecular device for sensing septin cytoskeleton organization.